Sp 



CONCHIFERA. 



197 



/. triangularis. Beau. Mag. Nat. Hist. N. Sor. III. p. 

 •in, fig, 20. 



Triangular, smooth, inflated ; beaks small, considerably in- 

 flpc'tcd ; surface with pretty strong, concentric lines of growth, 

 and [fine, somewhat regular, longitudinal stria) ; basal line 

 much arcuated. 



In the Cornbrash, Scarborough, Yorkshire. 



Jl. IsocARDiA ANGiLATA. — Tho Aogulated Isocardia, pi. 

 LXXIX. tigs. 2i, 25. 



/. angulata. Phillips, Geo. York, I. pi. 2, figs. 20, 21. 



Sub-triangular, beaks obtuse and large ; surface smooth ; 

 base very little curved, and rather acute at both extremities. 



The Specten Clay, Speeton, Yorkshire. 



12. IsocAKDiA RnoMBoiDALis. — The Rhomboidal Isocardia, 

 pi. LXXIX. fig. 16. 



/. rhomhoidalis. Phillips, Geo. York, I. pi. 3, fig. 28. 



Rhomboidal, or obliquely quadrate ; anterior side depressed ; 

 smooth ; posterior side with many narrow concentric furrows ; 

 basal line triangular. 



The Coral Rag, Jlalton, Yorkshire. 



1.3. Isocardia axiniformis. — The Axinus-formed Isocardia, 

 pi. LXXX. fig. G. 



/. axiniformis. Phillips, Geo. York, II. p. 209, pi. 5, f. 13. 



Transversely elongated, wedge-shaped ; beaks rather short 

 and involute ; surface glabrous, with many fine, concentric 

 stria?. 



The Carboniferous Limestone, Northumberland. 



14. Isocardia nitida. — The Shining Isocardia, pi. LXXX. 

 fig. 17. 



/. nitida. Phillips, Geo. York, I. pi. 9, fig. 10. 



Heart-shaped ; beaks involute ; surface smooth and shining. 



The Great Oolite, Coughton, Wyke. 



15. Isocardia tumida. — The Tumid Isocardia, pi. LXXIX. 

 fig. 15. 



/. tumida. Phillips, Geo. York, I. pi. 4, fig. 25. 



Heart-shaped, much inflated, rather elongated ; beaks tumid, 

 considerably involute ; surface with transverse lines of growth, 

 and crossed by longitudinal, radiating, shallow furrows, com- 

 mencing on the disk, and terminating in the basal margin all 

 round. 



The Calcareous Grit, Gristhorpe, Yorkshire. 



The Carboniferous Limestone, Dublin, Kildare, and Bol- 

 land, Yorkshire. 



Genus XVIII.— CARDIOMORPHA.—A'onmcit. 



Shell equivalve, inequilateral, frequently oblique, and trans- 

 versely elongated ; ventricose and heart-shaped ; hinge-line 

 straight, and extending from behind the beaks, and terminating 

 in a produced acute point ; hinge destitute of teeth ; insido 

 with two muscular impressions ; the pallial impression simple, 

 and destitute of a sinus ; texture of the shell thin. 



1. Cardigmorpiia onLo.NGA. — Tho Oblong Cardiomorpha, 

 pi. LXXIX. figs. 30, 31, and pi. LXXXI. fig. 5. 



C. oblonga. Koninck, p. 103, pi. 2, fig. 7. Isocardia ob- 

 longa. Sowcrby, V. p. U8, pi. 491, fig. 2. Phillips, Geo. 

 York, II. p. 209, pi. 5, fig. 9. 



Oblong, sub-compressed, anteriorly expanded, and very 

 short ; with the beaks close to and curved into it ; posterior 

 side large; hinge-line nearly straight ; surface smooth. 



Genus XIX.— OPIS.— Z)^ra«c«. 



Shell equivalve, rhomboidal, heart-shaped, inflated; beaks 

 involute and approximate, nearly touching ; hinge-area ob- 

 lique ; hinge with a large striated tooth, fitting into a cavity 

 in the opposite valve ; lunette very large, deep, oval, and 

 pointed below the cavity, which has two smaller teeth on 

 each side. 



1. Oris LUNULATA. — The Luniform Opis, pi. LXXX. 

 figs. 15, Ifi. 



Cardita lunulata. Soworby, III. p. 55, pi. 232, figs. 1, 2. 



Rhomboidal, inflated, and pointed anteriorly, and separated 

 by a projecting keel ; beaks involute, considerably produced ; 

 posterior side rounded, and with an incurved margin, which 

 confines the deeply excavated lunette, and strongly impressed 

 by the involute beaks ; anterior side furnished with a series of 

 steps, the first of which is somewhat concave, giving the mar- 

 gin a truncated aspect; right valve with two teeth, and one 

 in the left, which looks into a cavity between the two in the 

 opposite valve ; surface with transverse ribs ; base acute. 



The Groat Oolite, Cain's Cross, and the Inferior Oolite, 

 Dundry. 



2. Opis .similis.— The Similar Opis, pi. LXXX. fs. 13, 14. 

 Cardita similis. Sowerby, III. p. 56, pi. 232, fig. 3. 



Phillips, Geo. York, I. pi. 3, fig. 23. 



Gibboso, rhomboidal, anterior side separated by a produced 

 serrated keel ; lunette nearly heart-shaped, and almost flat ; 

 beaks involute ; surface transversely ribbed. 



Resemliling 0. lunulata, but the shell is shorter, more inflated; the 

 ribs less prominent on the sides, and the base not so acute. 



The Coral Rag, Malton and Scarborough, aud the Inferior 

 Oolite, Dundry. 



Genus XX.— SPILt:RA.—.S'oic«%. 



Shell bivalve, globular, with short, obtuse, incurved ears ; 

 with one ccntr.al and two (?) remote teeth about tho hinge, tho 

 lino of which is lengthened, slightly incurved, .and terminating 

 at one end with an indistinct tooth, beneath the insertion of 

 tho ear ; in its centre is a large irregularly-formed tooth, 

 transversely depressed, and pointing towards the incurved ap- 

 proximate beaks. It is a heavy shell, gibbose in its shape. 



I. Si'ii.EUA coRKUGATA. — The Corrugated Sphwra, pi. 

 LXXX. fig. 10. 



S. corrnffata. Sowerby, Min. Conch. IV. p. 42, pi. 335, 

 fig. 2. yentis Ringmcrcnsis. Mantell, Geo. Sussex, p. 1 26, 

 pi. 25, fig. 5. 



Shell gibbose, ponderous ; surface with coarse corrugations ; 

 ruga; placed transversely and obtuse, more conspicuous near 

 the sides, nearly smooth in the middle, but extending over the 

 ears. 



In the Iron Sand Formation, east of Sandown B.ay, Isle of 

 Wii'ht; and at Middlehara and Ringmcr, and the Lower 

 Greensand, Sandgate and Shanklin. 



