THE LAMELLIBRANCHIA 



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Hall ; Devonian and Carboniferous. Pseudomonotis, Beyrick ; Devonian 

 and Cretaceous. Cassianella, Beyrich ; Trias. Monotis, Bronn ; Trias. 

 Jkwnella, Mojsisovics ; Trias. Posidonomya, Bronn ; Silurian to Jurassic. 

 FAMILY 3. PRASINIDAE, Stoliczka. Shell inequilateral with anterior 

 unibones, and a prominent anterior auricula ; the dorsal border arched ; 

 the hinge with a single fossa and a single tubercule on each valve. 

 Genus Prasina, Deshayes. FAMILY 4. PTERINEIDAE, Goldfuss. Shell 

 thick, very inequilateral ; the cardinal border straight, with two auriculae 

 and a notch for the byssus under the right anterior auricula ; an extinct 

 family from the Palaeozoic. Genera Pterinea, Goldfuss ; Silurian to 

 Carboniferous. JRhombopteria, Jackson ; Silurian. Actinodesma, Sand- 



it m 



VI. C 



Avicula tarentina, Lamarck, from below, a, anus ; d, adductor muscle ; li.gr, byssal groove 

 of the foot ; by, byssus ; e, eye ; /, foot ; g, gill ; l.p, labial palp ; M, mouth ; pa, mantle ; sh, 

 shell ; vi.c, visceral commissure ; vi.g, visceral ganglion. (After Poli.) 



berger ; Devonian. FAMILY 5. LUNULICARDIIDAE, Fischer. Shell thin, 

 triangular, very inequilateral, the anterior end truncated ; the umbones 

 terminal ; the cardinal border straight ; without hinge teeth. An 

 extinct family from the Silurian and Devonian. Genera Lunuli- 

 cardium, Miinster ; Silurian and Devonian. Patrocardium, Fischer ; 

 Silurian. Babinka, Barrande ; Silurian. FAMILY 6. CONOCARDIIDAE, 

 Neumayr. Shell thick, subtriangular, the anterior side truncated and 

 gaping ; cardinal border straight and prolonged into two auriculae of 

 which the anterior is very long and narrow ; hinge with a lateral tooth 

 and a reduced cardinal tooth. Dimyarian. An extinct family from the 

 Palaeozoic. Genus Conocardium, Bronn ; Silurian to Carboniferous. 

 FAMILY 7. AMBONYCHIIDAE, Miller. Shell inequilateral, without an 

 anterior auricula, the umbones anterior and terminal ; hinge with two 



