48 
THE GEOLOGIST. 
Types with many Cartilage-pits. 
Gervilia . 
Macrodon 
Perna* 
F:4- 
•FQ.. + 
Types imth numerous Parallel Teeth. 
(i:+a = +)-i^ 
1: + 
1: + 
Area . . . ^— -7- ; liinge straight. 
Cucullsea 
+ . muscles 
margined 
by lamellae. 
Pectunculus ; hinge crescentic. 
. 1:+F-1: + 
1. 1: + -F-1:+ hinge 
angular at F. 
Nuculina ^ ~7t|-; ; hinge angular. 
Leda . . 
Solenella 
1; + -F-1: + 
1: + -F-1: + 
1: + "1: + 
;8. 
Types with few Teeth under the Umbo. 
Chama. . 
11 
Pholadomya — 
• 12 • 
Iphigenia . 7^0". 
Psammobia — ; S. 
• 2 • 
Astarte . ; L. 
J-. ; L ; keeled. 
Opis . 
Pachyrisma •• M (^^^ 
Gastrana. — — • s 
• 2 • ' 
1^ • 1 • 
Capsula . TYTjT. ; S. 
Sanguinolaria ~ ; S. 
Pharus. . 
•1:12 
; S. 
Solecurtus ■ S ; both ends gaping. 
Saxicava . 
Diplodonta 
2^ 
2* 
. 12 . 1 
Venericardia 
Trigonia . 
Lucinopsis 
1:12" 
2' 
111- 
1 :"2' • 
•2- 
1:12:1. 
Circe . . . ; L. 
3 
Venus . . L; S. 
Tapes . . s. 
Glaucomya ^ ^ ; S. 
Saxidomus ^ ; S. 
' 4 • 
Cytherea .-23^; S. 
4 . • ' ' . L ; S ; orbicular; si- 
Artemis . ^ 3 . > nus an elonga- 
ted cone. 
* In this genus should be included all the fossil species called Inoceramus, excepting 
perhaps /. involutus, which may be left as a critical subtype, having much the same re- 
lation with Perna that Janira has with Pecten. 
t The Palaeozoic species of Nucula and Leda have external ligaments, and are re- 
garded by authors as then forming one genus, which is named Ctenodonta. 
