series of thin edentulous Silurian shells, which Professor M'Coy has arranged provisionally in his genus Anodontopsis. There is no certainty that Pseudaxinus is related to Modiola, although Anodontopsis belongs to that group; and the presumption is against it. It may quite as likely be an edentulous form of Arcade.

Thin, edentulous, convex, with prominent umbones and a strong posterior carinated ridge; beaks anterior; no lunette. Surface smooth or only concentrically striate.

Types, P. (Anodontopsis) securiformis, M'Coy, and P. trigonus, here described.

7. PSEUDAXINUS TRIGONUS, spec. nov. Pl. XV. fig. 6.

Eleven lines long, and ten high; the depth of the united convex valves being 7 lines. Beaks very prominent, almost gibbous, from which a strong carina runs to the posterior angle. Anterior side very convex, rounded, somewhat oblique, with no lunette or depression beneath the beak; posterior side obliquely truncate, pointed, concave. Surface with fine concentric striæ.

HIPPOMYA, gen. nov. (Fam. MYTILID.E.)

A curious shell, whose affinities with the Mytilida I do not think doubtful, but which may probably indicate still more closely the relation between this group and the Arcade. In no living genera allied to Modiola is there so extensive a development of the foot and byssus as must have been here present, to give rise to the great horseshoe-shaped sinus on the anterior part of the ventral aspect. The typical Arcadæ (Byssoarca) have a somewhat similar character. Yet this is a thin shell, with close umbones and no trace of cardinal area, while the obscurity in our specimen of any muscular scars prevents a close comparison with the genera of either group. I cannot help suspecting that Modiolarca is its nearest ally*. The name may be understood to have only a general signification, and not to indicate any close relations with Mya. The shell does not gape at either end, except for the foot and byssus.

A gibbous shell, with anterior inflated close beaks, a long cardinal edge, but no area, not gaping at either end, the anterior side short, rounded, and separated by a strong sinus from the inflated posterior ridge and slope; surface with lines of growth only, no radii. Anterior margin, for nearly half the length of the shell, strongly incurved, and widely open for the passage of a large ovate byssus, which was probably very short, horny, and disk-like.

8. HIPPOMYA RINGENS, sp. nov. Pl. XV. fig. 7.

An inch and a quarter long by ten lines high, and depth of united valves fully one inch. The valves are obliquely trapezoidal-ovate, the posterior margin obliquely truncate above, the anterior equally truncate below and parallel to it. A regular gibbosity marks the posterior slope, greatest in the middle of the shell, which is decidedly

* See Woodward, Ann. Nat. Hist. 1856.

constricted behind the anterior or byssal portion, and is covered by lines of rugæ and lines of growth.

9. ORTHONOTA GRAMMYSIOIDES, sp. nov. Pl. XVI. fig. 10.

(Compare Cypricardia Ludoviciana, Rouault, Bull. Soc. Géol. Fr. 2nd ser. vol. viii. p. 374.)

Transverse oblong, rounded at both ends, with prominent curved beaks overhanging the thin edentulous hinge-line. A broad depression runs from the beak to the front margin, making the shell trilobed, and partially obliterating the strong concentric ruga which ornament the whole shell. These are very strong rounded ridges on the convex anterior portion, and become duplicated and interlined as they pass over the abrupt but not keeled umbonal ridge behind.

The ornaments on this pretty species (which, notwithstanding some discrepancies, closely resembles Rouault's shell from Gahard) recal those of Grammysia, to which the genus Orthonota is closely allied. The name is intended to express this affinity. M. de Verneuil thinks this, too, may be Devonian. I confess I do not. Cypricardia Mariana, Rouault, appears to belong to the same group, but has fine concentric ridges.

10. LYRODESMA CÆLATA, spec. nov.

Pl. XVI. fig. 7.

Ovate, 11 lines long by half an inch high at the slightly prominent beak, which is placed at the posterior? fourth, where the shell is widest. In advance of this the shell tapers rapidly, and the anterior? end is obtusely pointed, almost almond-shaped.

The surface is closely covered with fine lines of growth, but appears smooth. The muscular scars are deep, divided from the umbonal cavity by thick subcardinal ridges. The hinge-plate broad, and has beneath the beak six or seven radiating teeth, of which the posterior? one (that nearest the rounded end) is the largest.

11. ARCA? NARANJOANA, De Vern.? Pl. XVI. fig. 8. Bull. Soc. Géol. Fr. 2nd ser. vol. xii. 1855, pl. 26. fig. 12.

This agrees so well with De Verneuil's figure and description (except the hinge-area, which we cannot see) that I do not like to give a new name. It is a little shorter in proportion.

being an Arca.

12. PALEARCA† SECUNDA, spec. nov. Pl. XVI. fig. 9.

I doubt its

Nearly an inch wide, three-quarters high, and, with valves united, 4 lines thick. Subtrigonal-ovate, the beak placed at the anterior? fourth, pointed, but not incurved. Anterior and ventral margins well rounded, posterior truncate. Umbonal ridge angular, arched, leaving but a narrow vertical anterior slope. Lunette? Hinge* I am not sure that the Lyrodesma falls into the usual character of the Nucule in having the beak posterior.

For the characters of this genus see Billings's Reports (under Cyrtodonta), 1857, and the Memoirs of the Geol. Survey Canada, vol. iii. (ined.).

area much arched, furnished with four or five oblique teeth, which are all in the same direction; hence the name. There are three distinct and very oblique nearly transverse teeth in front of the beak, and behind it one long cardinal tooth in each valve, as indicated by the cast. This long tooth reaches to the extremity of the arched hinge-line, and is quite parallel to the margin. The others radiate more or less, not from the beak outwards (as in the Lyrodesma, just described) but from the lower edge of the hingeplate; the muscular scar in front is large and round, the hinder one elongated.

The subtrigonal shape distinguishes this easily from all the Canadian species (Geol. Canada, 1863, p. 147, &c.). None of the British species have so narrow and pointed a posterior end.

13. CTENODONTA BERTRANDI, Rouault, sp. Pl. XV. fig. 8.

Nucula Bertrandi, Rouault, Bull. Soc. Géol. Fr. 2nd ser. vol. iv. 1846-47, p. 322.

I do not feel certain of this identification, but M. de Verneuil, in his letter to me, admits it.

14. SOLEN? (or some allied genus). Pl. XVI. fig. 11.

There are, besides the above, a Strophomena somewhat allied to S. compressa, Sil. Syst.,' and of about the same size, plano-convex in form; two species of Bellerophon; an Orthoceras with close septa and a nearly lateral siphon, and one or two other smooth species of the same genus; and several undescribed Lamellibranchiata, which must await illustration at some future opportunity.

EXPLANATION OF PLATES XV., XVI., XVII.

Illustrative of Fossils from Budleigh Salterton.
PLATE XV.

Fig. 1. Homalonotus Brongniarti, Deslongchamps, sp. a, glabella and fixed cheeks; b, free cheek; c, thorax-joint; d, tail, showing serrate margin.

2. H. Brongniarti, var. with somewhat squarer outline to head.

3. Homalonotus, sp. not yet described in France or England.

4. Phacops incertus, Deslongch., sp. a, interior cast of head; b, exterior mould, in gutta-percha, of the tail-piece.

5. Calymene Tristani, Brongn. Interior cast of tail.

6. Pseudaxinus trigonus, Salter. Two views of an interior cast of the right valve of a thin shell.

7. Hippomya ringens, Salter: a, dorsal view; b, ventral view, showing the passage for the huge byssus.

8. Ctenodonta Bertrandi, Rouault: a, interior of right valve; b, magnified surface.

9. Trachyderma serrata, Salter: a shows the projecting squamose ridges of the tube; b is a rough interior cast.

PLATE XVI.

Fig. 1. Modiolopsis Armorici, spec. nov.: a, cast of interior, right valve; b, dorsal view of broken pair of valves.

2. Modiolopsis, sp.: cast of left valve, and edge-view of ditto.

Fig. 3. Modiolopsis obliquus, spec. nov.: a, interior cast of left valve; b, restored figure; c, right valve of young specimen.

4. Modiolopsis liratus, spec. nov.: left valve, interior cast, and edge-view of the same.

5. Modiolopsis lingualis, spec. nov. right valve, interior cast.

6. Clidophorus? amygdalus, spec. nov.: a, interior cast of right valve; b, edge-view; c, restored hinge from gutta-percha cast.

7. Lyrodesma calata, spec. nov.: a, interior of right valve; b, hinge, cast in gutta-percha from a.

8. Arca? Naranjoana?, De Verneuil. Right and left valves, interior casts. 9. Palæarca secunda, spec. nov.: a, interior cast of left valve; b, edgeview; c, hinge, cast in gutta-percha from a.

10. Orthonota Grammysioides, spec. nov.: a, right valve; b, edge-view. 11. Solen?, sp. Imperfect external impression of right valve.

PLATE XVII.

Fig. 1. Lingula Lesueuri, Rouault.

2, 3. L. Hawkei, Rouault. Both valves, and edge-view of the same. 4, 5. L. Rouaulti, spec. nov. Upper and lower valves: 4a, edge-view of united valves.

6. L. Brimonti, Rouault. Smaller valve.

7. Orthis redux, Barrande: a, b, interior casts of dorsal valve; c, interior casts of ventral valve.

7d. Variety with deeper furrows, dorsal valve.

8. Orthis pulvinata, spec. nov. Interior dorsal_valve.

9. Porambonites, sp.

10, 11. Spirifer antiquissimus, spec. nov. Interior casts of dorsal valve: 10 a, edge-view of ditto.

12. Interior cast of ventral valve of ditto.

13. S. Davidis, Rouault? Interior of dorsal valve.

14. Rhynchonella, SP. Possibly Devonian forms.

15.

sp.

16, 17. Leptæna Vicaryi, spec. nov.: 16 a, b, two views, internal cast of the deep ventral valve; 17, cast of external surface of the concave smaller or dorsal valve.