48 



THE GEOLOGIST. 



Types tvith many Cartilage-pits. 



Gervilia . 



Macrodon 



•F Q- + 



Perna* . 



numerous Parallel Teeth. 



1: + 

 1: + 



Area . . . ^— r ; hinge straight. 



Cucullsea 



+ . muscles 



l:-}-*'l:-f- margined 

 by lamellae. 



Pectunculus . hinge crescentic. 



T . . 1:+F-1: + 

 Limopms. 1; + Jj ,. 1; + 



AT . , 1 : + • F • 1 : + hinge 

 NuCUlat ' l: + -F-l: + ; sharply 



angular at F. 



Nuculina \ '4" — i ; hinge angular. 



Leda . . 



1: + "1' 

 1: + -F'1: + 



i s. 



Solenella ^ ; + .".^ + ;S. 



Chama. . 



11 



fOtVA /<?w Tee^A wwefer the Umbo. 



Saxicava . 



Pholadomya — 



l 2 



Iphigenia . -p-. 



Psammobia — - ; s. 



• 2 



• 2 * 



Astarte . — ; ,L. 



Opis ... ; L ; keeled. 

 Pachyrisnia •• 



Gastrana. 



I 2 



1 2 :1 



Capsula . . 1 ' 12 , ; S. 



* 2 * 



Sanguinolaria — j S. 



Pharus 



2 • 



Solecurtus — . S ; both ends gaping. 



Diplodonta ^ ^ - 



•2- 

 111; 



l:~2 lT 



Venericardia 

 Trigonia . 



Lucinopsis 1 f * : ' 1 ; S. 



Circe . . . A ; L. 

 3 



Venus . . 



;L;S. 



Tapes • • ; 3 . ; S. 



Glaucomya - 



3 



2:1- 



s. 



Saxidomus —r 1 S. 



• 4 • ' 



Cytherea r^-j L ; S. 



. L ; S ; orbicular ; si- 



Artemis 



23 



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, haviug 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. 



