458 



EULAMELLIBRANCHIATA ANATINACEA 



within the branchial siphon, siphons veiy long, with two cal- 

 careous appendages (" pallets ") near the anterior end, shell very 

 small, continued into a long calcareous tube, valves deeply notched, 



internal apophysis as in Pholadidae. Lias . Single 



genus. Teredo (Fig. 310). 



Sub-order VII. Anatinacea. — External branchial fold directed 

 dorsally, not reflected, sexes united, ovaries and testes with sepa- 

 rate orifices, mantle edges largely united, byssus usually absent, 

 two adductor muscles, pallial liue variable, shell usually nacreous 

 within. 



Fam. 1, Fandoridae. — Siphons short, largely united, foot 

 tongue-shaped ; shell free or fixed, inequivalve, semilunar, or 

 subtriangular, ligament often with calcareous ossicle, pallial line 



complete or with slight sinus. 



Cretaceous . Genera : Fan- 



dora, Myodora, Afyochama. 



Fam. 2. Chaviostreidae. — Shell 

 fixed, Chama-\\\\.Q, thick, umbones 

 spiral, ligament with ossicle. 

 Single genus, Chamostrea. 



Fa:\i. 3. Verticordiidae. — - 



Siphons not prolonged ; shell 



heart-shaped, umbones prominent, 



spiral, ligament with an ossicle. 



Fig. Zll.—Myochama Stutchhuryi A. pallial line Complete. Miocene 



. Genera : Verticordia, 



Mytilimeria, Lyonsiella. 

 Fam. 4. Lyonsiidae. — Foot short, Ijyssiferous, siphons short, 

 separate, shell inequivalve, hinge teeth usually absent, ligament 



and ossicle in an internal o-roove. Eocene . Single genus, 



Lyonsia. 



Fam. 5. Ceromyidae. — Shell inequivalve, large, heart or wedge- 

 shaped, hinge toothless, ligament internal in one valve, external 



in the other. Secondary strata . Genera : Ccromya, Gresslya. 



Fam. 6. Arcomyidae. — Shell equivalve, thin, surface finely 

 granulated, hinge toothless, cardinal edge dentiform, ligament 



external. Secondary and Tertiary strata . Genera : Arcomya, 



Goniomya, Pleuroviya, Maclunnya. 



Fam. 7. Anatinidae. — A fourth (? byssal) pallial orifice, siphons 

 long, separate or fused ; shell thin, sometimes inequivalve, exterior 



Ad., attached to Circe undatina 

 Lam., Moretou Bay. 



