COl^GRYLIA—DITHYRA. xiH. 



32. Capsa. — Testa cuneata, ligamento ad latus brevissimum. 



Shell wedge-shaped, with the ligament at the 



shortest side. 

 17. Agina. — Testa transversa, dente conico in utrdque valvd. 



Shell transverse, with a single conic tooth in 



each valve. 

 30. Ceyptodon. — Testa trigono-globosa, dente unico obsoleto in 



utrdque valvd cum fovea transversd. 



Shell triangular-globular, with a single obscure 



tooth in each valve and a transverse cavity. 

 26. PsAMMOBlA. — Testa oblonga vel ovata, lateribus subhiantibus, 



dentibus subbinis. 



Shell oblong or oval, a little open at the sides, 



with two teeth in one or both the valves. 

 5. HiATELLA. — Testa inaeqidvalvis, medio vel latere antico kiante, 



dente unico inter duos penetrante. 



Shell ineqnivalve, open in the middle or at the 



anterior end, with a single tooth in one valve 



closing between two in the other. 

 33. Ceassina — Testa clausa, dentibus duobus in utrdque valvd. 



Shell closed, with two teeth in each valve. 

 28. LuciNA. — Testa clausa, dentibus duobus vel tribus cum foveold 



laterali transversd. 



Shell closed, with two or three teeth and a 



lateral transverse hollow. 



