204 



CONCHIFERA. 



The Cornbrash, Scarborough. 



4. PoLLASTRA viRGiNEA. — The Virgin PuUastra, pi. 



Lxxxiir. fig. 1. 



p. virginea. Brown, Illust. Rec. Conch. Brit. p. 89, pi. 

 36, fig. 6, and pi. 37, figs. 8, 9. 



Oblong-ovate; sub- compressed ; smooth and shining, with 

 wide- set, shallow, concentric striae, here and there interrupted 

 by a deeper one ; lunule lanceolate ; margins smooth. 



The Pleistocene Marine Formation, Ayrshire, and the Red 

 Crag, Sutton. 



5. PuLLASTRA DECUSSATA. — The Decussated Pullastra, pi. 



Lxxxiii. fig. e. 



p. di'cussata. Brown, Illust. Rec. Conch. Brit. p. 88, pi. 37, 

 figs. 5, 6. 



Transverse, inequilateral; anterior side shortest ; sub-rhom- 

 boidal ; anterior side a little truncated ; whole surface covered 

 with longitudinal and transverse strise, producing a beautiful 

 and decussated appearance, which is stronger on the anterior 

 side; beaks obtuse, with a lanceolate lunule. 



The Pleistocene Marine Formation, Ayr and Paisley. 



6. Pullastra oblita. — The Forgotten Pullastra, pi. 

 LXXXIII. fig. 5, 



P. oblita. Phillips, Geo. York, I. pi. 11, fig. 15. 



Transversely oblong-ovate ; anterior side acutely rounded ; 

 posterior side slightly flattened and acuminated ; beaks 

 obtuse ; surface with almost equidistant regular lines of 

 growth. 



The Inferior Oolite, Blue Wick, Yorkshire. 



7. Pullastra becondita. — The Hidden Pullastra, pi. 

 LXXXIII. fig. 11. 



P. recondka. Phillips, Geo. York, I. pi. 9, fig. 13. 



Transversely ovate ; both extremities rounded ; a central 

 ridge from the beak to the margin ; whole surface with nume- 

 rous concentric furrows ; beaks small. 



The Great Oolite, Cloughton, Wyke and Brora. 



8. Pullastra elliptica. — The Elliptical Pullastra, pi. 

 LXXXIII. fig. 12. 



P. elliptica. Phillips, Pal. Foss. p. 35, pi. 17, fig. 54. 

 Regularly ovate, much compressed ; beaks hardly protrud- 

 ing ; surface smooth, with wide-set concentric striae. 



9. Pullastra antiqua. — The Ancient Pullastra, pi. 

 LXXXII. fig. 10. 



P. antiqua. Sowerby, Geo. Tr. 2d Ser. V. pi. 53, fig. 28. 

 Phillips, Pal. Fos- pi. 17, fig. 55. 



Transversely oblong-ovate; moderately convex; anterior 

 side rounded ; posterior side slightly and obliquely truncated ; 

 beaks scarcely developed ; surface with regular wide-set con- 

 centric striae. 



The Devonian Rocks, Pilton, Marwood, and Plymouth. 



10. Pullastra irus. — The Stone Pullastra, pi. LXXXIII. 

 fig. 13. 



P. irus. Brown, Illust. Rec. Conch. Brit. p. 89, pi. 36, 

 fig. 9. Venirupus perforans, Turton, Biv. p. 29, pi. 2, figs. 

 15-18. 



Transversely sub-ovate ; surface with concentric, membran- 

 aceous, elevated, undulating ridges, reflected upwards, fre- 

 quently interrupted; the interstices with fine longitudinal 

 atrise. 



The Red Crag, Walton Naze. 



Genus XXIX.— VENUS.— ZiwjzfCMS. 



Shell smooth, equivalve, inequilateral, transverse, subglo- 

 bose, or sub-oval ; external surface sometimes rugose ; margin 

 close ; three divergent cardinal teeth in each valve, all approxi- 

 mate ; umbones prominent for the most part, with a cordi- 

 forni depression immediately below them ; two lateral, remote, 

 somewhat orbicular muscular impressions, united by a pallial 

 impression, which is generally sinuated behind ; ligament ex- 

 ternal, although sometimes almost hidden by the extension of 

 the outer edge of the shell. 



1. Venus submersa. — The Bulged Venus, pi. LXXIV. 

 fig. 2. 



V. submersa. Sowerby Geo. Tr. 2d Ser. IV. p. 342, pi. 

 17, fig. 4. 



Nearly orbicular ; extremely tumid ; beaks approximate ; 

 lunette obscure ; hinge slope gently curved ; posterior side a 

 little truncated ; surface quite smooth. 



The Greensand, Blackilown. 



2. Venus sub-L/EVis. — The Half-Smooth Venus, pi. 

 LXXXIV. fig. 8. 



r. stih-hccis. Sowerby, Geo. Tr. 2d Ser. p. 342, pi. 17, f. 5. 



Elliptical, compressed ; beaks pointed, situate near to one 

 side ; lunette not sunk or defined ; surface smooth, with a few 

 shallow, hardly impressed lines of growth. 



The Greensand, Blackdown. 



3. Venus immebsa. — The Immersed Venus, pi. LXXXIV. 

 fig. 9. 



V. immersa. Sowerby, Geo. Tr. 2d Ser. IV. p. 342, pi. 

 17, fig. 6. 



Transversely elliptical ; much compressed ; beaks consider- 

 ably acute; lunette deeply sunk, its edge not defiued ; back 

 and base elegantly curved ; posterior side a little narrowed ; 

 anterior side a little concave below the beaks ; surface smooth, 

 with remote, nearly obsolete lines of growth. 



The Greensand, Blackdown and Lyme Regis. 



4. Venus ovalis.— The Oval Venus, pi. LXXXIV. f. 16. 

 V. ovalis. Sowerby, VI. p. 129, pi. 567, figs. 1, 2. 

 Transversely oval ; convex ; beaks well defined ; lunette 



obscure, elongated, prominent, and smooth ; surface with 

 numerous very fine concentric striae. 

 The Lower Greensand, Parham. 



5. Venus varicosa. — The Warted Venus, pi. LXXXIV. 

 fig. 17. 



V. varicosa. Sowerby, III. p. 173, pi. 296, figs. 1, 2. 



Sub-globose ; beaks large, produced, and incurved ; sides 

 nearly alike ; surface with shallow, concentric furrows, and 

 two longitudinal varicose ridges within each valve. 



The Cornbrash, Felmersham, Bedfordshire. 



6. Venus bugosa. — The Rough Venus, pi. LXXXIV. f. o. 

 V. riiffosa. Brown, Illust. Recent Conch. Brit, and Ire- 

 land, p. 90, pi. 36, fig. 14. 



Sub-triangularly sub-cordiform ; rather convex; lunette ob- 

 long, heart-shaped ; beaks considerably turned to one side ; 

 surface with numerous rough concentric ridges ; a hollow 

 elongated space on the cartilage hinge-line ; margin blunt, 

 and crenated internally. 



The Pleistocene Marine Formation, Dalniuir, on the Clyde, 

 &c. 



