GLAUCOMYID^. 183 



LiocYMA, Dall, 18t0. 



Distr. — 2 sp. L.Jluctuosa, Gould (cxxiii, 87). 



Shell small, ovate, concentrically striated, compressed, nearly 

 equivalve and rather thin ; there are in each valve three cardinal 

 teeth, the middle one cleft ; pallial sinus small. 



Baroda, Stoliczka, 1870. 



Distr. — B.fragilis, d'Orb. (cxxi, 1-3). Cretaceous. 



Shell very much elongated, very inequilateral, with subparallel 

 upper and lower margins laterally compressed, pallial sinus 

 moderate, horizontal or nearly so, obtuse at the end ; hinge with 

 three cardinal teeth in each valve, the posterior of which is very 

 much elongated and sometimes longitudinally furrowed ; the 

 two other teeth sometimes appear as one widely bifid tooth ; 

 surface of valve smooth, only with concentric striae of growth. 



ICANOTIA, Stoliczka, 1869. Form similar to the last, inner 

 edge of the shell anteriorly somewhat thickened, surface covered 

 with radiating strige and ribs, strongest on the posterior upper 

 slope. Psammobia impar, Zittel. 



Family GLAIJCOMYID^. 



Shell transverse, with a greenish epidermis. Siphons very 

 long, compressed, united nearly to the extremity'-, which is fringed ; 

 foot large, linguiform, compressed, subcarinated. 



Glaucomya (Bronn), Gray. 



Etyrti. — Glatwos, sea-green ; mya, mussel. 



Syn. — Glauconome, Gray, 1829 (not Goldfuss, 1826). 



Distr. — 16 sp. Embouchures of rivers ; China, Philippines, 

 Borneo, India. Fossil, 2 sp. Tertiary ; Europe. G. rugosa, 

 Reeve (cxii, 3-5). 



Shell oblong, thin ; epidermis dark, greenish ; ligament exter- 

 nal ; hinge with three teeth in each valve, one of them bifid ; 

 pallial sinus very deep and angular. 



Animal with a rather small, linguiform foot ; pedal opening 

 moderate ; siphons very long, united, projecting far into the 

 branchial cavity when retracted, their ends separate and diver- 

 ging ; palpi large, sickle-shaped ; gills long, rounded in front, the 

 outer shortest. 



TANYSiPHON, Bcnson, 1855. Siphons united to the end ; hinge 

 with three teeth in the right and two in the left valve ; pallial 

 sinus very deep. Calcutta, buried in mud at extreme low- water. 

 O. rivaliSj Benson (cxii, 1,2). 



Suborder INTE GBIPA LLIA TA . 



Siphons short, not retractile ; the pallial impressions simple 

 usually without siphonal sinus. 



