BY E. M. JOHNSTON, F.L.S. 



109 



Genus Dosinia. (632-636.) 

 Shell orbicular, compressed, concentrically striated, pale, ligament 

 sunk ; lunule deep ; hinge like Cytherea, margins even ; 

 pallial sinus deep, angular, ascending. Dist. — Boreal, 

 Tropical Seas. Low water, 80 fathoms. 



Sub-Genus Got/ldia. 

 Shell sub-trigonal, oval, smooth, shining, inflated. 



Genus Tapes. (637.) 

 Shell oblong, umbones anterior, margins smooth ; teeth, three 

 in each valve, more or less bifid; pallial sinus deep, 

 rounded. Dist. — Norway, Britain, Black Sea, Senegal, 

 Brazil, India, China, New Zealand. Low water, 100 

 fathoms. 



(Ixxxi.) Family Cyeenid^!. 

 Shell sub -orbicular, closed, ligament external ; epidermis thick, 

 horny ; umbones of aged shells eroded ; hinge with 

 two or three cardinals and lateral teeth ; pallial line 

 with a small inflection. 



Genus Coebioula. (638.) 

 Shell sub-cordiform, solid, close, concentrically striated or 

 rigid, covered by a smooth, greenish epidermis ; three 

 cardinal teeth in each valve, the right anterior and 

 left posterior rather small ; lateral teeth elongated, 

 compressed, striated ; ligament prominent, thick ; 

 pallial impression with a slight or well-marked sinus. 

 Dist. — India, Bast Indies, Philippines, S. America. 



Genus Pisiditjm. (639-640.) 

 Shell sub-oval, trigonal, inequilateral, covered by a greenish 

 epidermis ; cardinal teeth very small, elongated, one 

 sometimes bifurcated in the right valve, two diverg- 

 ing in the left valve ; lateral teeth longitudinal, com- 

 pressed, lamelliform, double in the right valve. Dist. — 

 Universal. Fresh water lakes and rivers, Tasmania. 



Genus Sphjebium. ( 41.) 

 Syn. Cyclas. 

 knell thin, oval or sub-orbicular, inflated, covered by a greenish 

 epidermis ; cardinal teeth very small or rudimentary, 

 one more or less bifurcated, one in the right and two 

 oblique ones in the left valve ; lateral teeth compressed, 

 lamelliform, the anterior shortest ; ligament short ; 

 margins plain, muscular impressions scarcely apparent, 

 sub-marginal ; pallial impression simple. Dist. — 

 Universal. 



