ibo 



CONCHIFERA. 



U? 



xio. 



line very straight ; uiubones a little rugose, very small, and 

 contiguous ; posterior slope shorter, more pointed than the 

 anterior one, which is obliquely sub-truncated and a little 

 pointed at the extremity ; basal line slightly hollow ; length 

 about equal to half its width ; thickness three eighths of an 

 incli ; surface smooth, with indistinct, transverse undulations, 

 and of a pearlaceous tinge. 



Found in the Crag at Hordwell. 



35. UiNio coMPRESsus. — The Compressed Unio, pi. 

 LXXIII. fig. 11. 



U. compressus. Sowerby, VI. p. 189, pi. oO-i, fig. 2. 



Shell ovate, compressed ; umbones nearly central, and a 

 little produced ; hinge-line slightly arcuated ; length two- 

 thirds its breadth. 



Found in the Clay of Tilgate Forest. 



36. Unio antiquus. — The Ancient Unio, pi. LXXIII. 

 fig. 12. 



U. antiquus. Sowerby, Min. Conch. VI. f. 190, pi, 59-1, 

 figs. 3, i. 5. 



Shell elongated, transversely ovate ; beaks somewhat pro- 

 duced and sub-corapressed ; posterior side short, rounded ; an- 

 terior side elongated and sub-acute ; hinge-line straight ; sur- 

 face smooth. 



Found in the Weald Clay, Tilgate Forest. 



37. Unio porrectus. — The Extended Unio, pi. LXXIV. 

 fig. 14. 



U. porrectus. Sowerby, Min. Cone. VI. p. 180, pi. 594, f. 1. 



Shell sub-compressed, much elongated ; beaks placed mucli 

 to the posterior side, which is rounded ; anterior side greatly 

 elongated, obliquely sub-truncated, and pointed below ; hinge- 

 line nearly straight ; length about half its width ; surface con- 

 vex and smooth. 



Found in the Limestone of Tilgate Forest. 



38. Unio polmontensis. — The Polmont Unio, pi. LXXIII. 

 figs. 32, 33. 



U.—{?) Rhind, Age of the Earth, p. 167, pi. 2. figs, c, d. 



Oblong ; umbones nearly central, somewhat acute, and re- 

 mote; hinge-line straight, posterior slope but little more 

 rounded than the anterior one ; surface smooth, with a few 

 nearly obsolete transverse furrows. 



Found iu the Coal Shale at Polmont, by "William RhinJ, 

 Esq. Surgeon, Edinburgh, and in his cabinet. 



39. Unio aduncus.— The Crooked Unio, pi. LXXIV. f. 1. 

 U. aduncus. Mantell, Foss. of Tilgate Forest, p. 57, pi- 



10, fig. 11. Sowerby, Min. Conch. VI. p. 190, pi. 595, f. 2. 

 Shell cuneiform, inflated, very thick ; umbones rounded ; 

 posterior slope very short ; anterior slope long, straight above, 

 sub-truncated, concave, and slightly bent downwards ; length 

 somewhat more than half its breadth. 



Found in the Wealden Clay, Tilgate Forest. 



40. Unio Walterii.— Walten's Unio, pi. LXXIV. f. 2, 3. 

 U. Walterii. Sowerby, Geo. Trans. 2d Ser. IV. p. 346, pi. 



21, fig. 16. 



Shell compressed, nearly square ; anterior slope rounded ; 

 posterior side slightly eared ; surface almost smooth, with a 

 few transverse, nearly obsolete wrinkles ; a central longitudi- 

 nal depression, emanating from the back of the umbones, ex- 

 tends to the basal margin. 



Sowerby sajs this depressiou is not a constant character. 



In the Weald, Lenthington, Tunbridge. 



41. Unio pictorum.— The Painter's Unio, pi. LXXIV.* 

 figs. 1, 2, and pi. LXXXVIII. fig. 8. 



U. pictorum. Brown, Land and Fresh-water Conch. Brit, 

 pi. 19, figs. 1, 2, 3, 4. 



Transversely oblong-oval, veutricose ; beaks a little pro- 

 duced ; hinge-line somewhat curved ; anterior side short and 

 rounded, posterior side elongated and acuminated ; hinge, 

 with a strong, double, compressed, elevated, elongated, arcuat- 

 ed cardinal tooth in the left valve, with a perpendicularly 

 striate<l papillose one behind, on which the tooth of the opposite 

 valve rests ; lateral teeth in both valves long and narrow : 

 surface with shallow, transverse undulations. 



The Pleistocene Fresh- water Formation at Cropthorn, 

 Feversham, Bacton and Grays. 



42. Unio (?) Austicei.— Austice's Unio, pi. LXXXVIII. 

 figs. 25, 27. 



U. Austicei. Sowerby, Geo. Tr. 2il Ser. V. pi. 39, fig. 7. 



Transversely elongated, sub-quadrate, and very convex ; 

 hinge-line a little bent ; beaks very obtuse, rounded, and ap- 

 proximate ; anterior side obliquely truncated and short ; pos- 

 terior side rounded ; beaks curved ; basal line nearly straight ; 

 surface with concentric wrinkles, and slight indications of ra- 

 diating, longitudinal striae. 



The Coal Measures, Coalbrook Dale, Staffordshire. 



43. Unio Urix.— Ures Unio, pi. LXXXVIII. figs. 9, 10. 

 U. Urii. Fleming, Brit. .Vn. p. 417. Sowerby, Geo. Tr. 



2d Ser. V. pi. 39, fig. 6. Ure's Hist. Rutherglen and Kil- 

 bride, p. 311, pi. 16, fig. 4. 



Greatly elongated transversely; very convex; hinge-lino 

 nearly straight ; beaks much depressed ; anterior side short ; 

 posterior side much elongated, and ratlier acute at its lower 

 termination ; back and basal lines straigiit and nearly parallel; 

 surface with rough, transverse undulations. 



The Coal Measures, Rutherglen, Renfrewshire, and Coal- 

 brook Dale, Staffordshire. 



44. Unio modiolaris. — The Modiola-shaped Unio, pi. 

 LXXXVIII. figs. 5, 6. 



U. modiolaris. Sowerby, Geo. Trans. 2d Ser. V. pi. 3!), 

 fig. 10. 



Transversely elongated ; convex ; anterior side short and 

 narrow ; posterior side lengthened, deep, and rounded ; beaks 

 very obtuse ; hinge-line straight ; back quite straight ; base 

 a little curved, and nearly parallel to the back ; a slight ele- 

 vation exteuils from the beaks to the posterior side ; surface 

 nearly smooth. 

 . The Coal Measures, Coalbrook Dale, Staffordshire. 



45. Unio acutus. — The Acute L'nio, pi. LXXIV. fig. 13. 

 U. acutus. Sowerby, I. p. 84, pi. 23, figs. 5, 6, 7. 



Transversely elongated ; anterior side short, rouuded, and a 

 little pointed towards the centre ; posterior side much elon- 

 gated, acuminated, and rounded ; hinge-line nearly straight ; 

 beaks considerably incurved, with the points approximating ; 

 surface smooth, with a few concentric shallow wrinkles. 



The Coal Measures, Bradford. 



46. L^Mo CENTRALIS. — The Central-beaked Unio, pi. 

 LXXXVIII. fig. 15. 



U. centralis. Sowerby, Geo. Tr. 2d Ser. V. pi. 39, Hg. 13. 

 Oval ; anterior side rather shorter than the posterior side. 



