180 
CONOHIFEAA. 
Unio. 
line very straight; umbones 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 lino slightly hollow; length 
about equal to half its width; thickness throe eighths of an 
inch ; surface smooth, with indistinct, transverse undulations, 
and of a pearlaceous tinge. 
Found in the Crag at Hordwell. 
35. Unio compressus. —The Compressed Unio, pi. 
LXXIII. fig. 11. 
U. compressus. Sowerby, VI. p. 189, pi. 594, 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. 594, 
figs. 3, 4. 5. 
Shell elongated, transversely ovate; beaks somewhat pro¬ 
duced and 8ub-compressed ; 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. 189, pi. 594, f. 1. 
Shell sub-compressed, much elongated; beaks placed much 
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, Ago 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 auterior one; surface smooth, with a few 
nearly obsolete transverse furrows. 
Found in the Coal Shale at Polmont, by William Rhind, 
Esq. Surgeon, Edinburgh, and in his cabinet. 
39. Unio aduncus. —The Crooked Unio, pi. LXXIV. f. 1. 
U. aduncus. Mantel 1, Foss, of Tilgate Forest, p. 57, pi. 
10, fig. 11. Sowerby, Min. Couch. 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.—W alten 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 slopo 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 umboues, ex¬ 
tends to the basal margin. 
Sowerby says this depression is not a constant character. 
In the Weald, Lenthington, Tunbridge. 
41. Unio pictorum. —The Painter's Unio, pi. LXXIV." 
figs. 1, 2, and pi. LXXXV11I. fig. 8. 
U. pictorum. Brown, Laud 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, olovated, elongated, arcuat¬ 
ed cardinal tooth in the left valve, with a perpendicularlv 
striated 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, 
Fevershaui, Bacton and Grays. 
42. Unio (?) Austicei. —Austice's Unio, pi. LXXXVIII. 
figs. 25, 27. 
U. Austicei. Sowerby, Geo. Tr. 2d 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 stri;e. 
The Coal Measures, Coalbrook Dale, Staffordshire. 
43. Unio Urii. —Ure's Unio, pi. LXXXVIII. figs. 9, 10. 
U. Urii. Fleming, Brit. An. p. 417. Sowerby, Geo. Tr. 
2d Ser. \ . pi. 39, fig. 6. Ure's Hist. Rutherglen and Kil¬ 
bride, p. 311, pi. 16, fig. 4. 
Greatly elongated transversely; very convex; hinge-line 
nearly straight; beaks much depressed; anterior side short; 
posterior side much elongated, and rather acute at its lower 
termination ; back and basal lines straight 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. 39 , 
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 extends from the beaks to the posterior side; surface 
nearly smooth. 
The Coal Measures, Coalbrook Dale, Staffordshire. 
45. Unio acutus* —The Acute Unio, pi. LXXIV. fig. 13 . 
U. acutus. Sowerby, I. p. S4, pi. 23, figs. 5, 6, 7. 
Transversely elongated ; anterior side short, rounded, and a 
little pointed towards the centre; posterior aide 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. Unio centralis. — The Central-beaked Unio, pi. 
LXXXVIII. fig. 15. 
U. centralis. Sowerby, Geo. Tr. 2d Ser. V. pi. 39, tig. 13. 
Oval; anterior side rather ^shorter than the posterior side, 
