THE LAMELLIBRANCHIA 261 
Hall ; Devonian and Carboniferous. Pseudomonotis, Beyrick ; Devonian 
and Cretaceous. Cuassianella, Beyrich ; Trias. Monotis, Bronn; Trias. 
Daonella, Mojsisovies; Trias. Posidonomya, Broun ; Silurian to Jurassic. 
FamILy 3. PRrastnipan, Stoliczka. Shell inequilateral with anterior 
umbones, 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. Famity 4. PrertnerpAn, 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. Rhombopteria, Jackson; Silurian.  Actinodesma, Sand- 
ULM 
g 
Se 
aes 
CARTES A 
aes 
Sea 
= 2 
Fie 236. 
Avitula tarentina, Lamarck, from below. a, anus; ad, adductor muscle ; b.gr, byssal groove 
of the foot ; by, byssus; ¢, eye; f, 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. FAmIty 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, Minster; Silurian and Devonian. Patrocardiwm, Fischer ; 
Silurian. Babinka, Barrande; Silurian. Famiiy 6. CoNnocarprpag, 
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—Oonocardiwm, Bronn ; Silurian to Carboniferous. 
Famity 7. AMBONYCHIIDAE, Miller. Shell inequilateral, without an 
anterior auricula, the umbones anterior and terminal ;, hinge with two 
