ISOCARDIIDiE. 191 



Cypricarclia is distinguished by the simple form of its hinge ; it 

 is based upon a cretaceous species, Gpr. carinata. 



GLOSSOCARDIA, Stolicz., 1870. Shell elongately trapezoid, sub- 

 ventricose, concentrically striated, beaks tumescent, obtuse, close 

 together as in C^^pricardia ; ligamental farrow narrow and long 

 as in Isocardia ; hinge with two cardinal and one posterior lateral 

 tooth in each valve ; the supero-posterior cardinal teeth generally 

 are more or less distinctly bifid, at least the one in the right 

 valve, which has anteriorly a thin, subobsolete prolongation 

 bent downward ; it is separated from the inferior cardinal and 

 bluntly tubercular tooth by a deep sickle-shaped groove, into 

 which fits the similarly shaped autero-inferior cardinal tooth of 

 the left valve ; this tooth is provided on the upper side with two 

 grooves, their distance being equal to the width of the pit into 

 which the antero-inferior tooth of the right valve fits. C. obesa, 

 Reeve (cxiv, 51). Mauritius. 



MiCRODON, Conrad, 1842. (Cypricardella, Hall. Eodon, Hall, 

 1817.) Shell ovate, subelliptical, or subquadrate ; concentrically 

 striated ; hinge of right valve with two cardinal teeth ; the 

 anterior tooth beneath the beaks ; posterior tooth turned 

 obliquely backwards, leaving a triangular pit, which is probably 

 occupied by a tooth inthe other valve. Anterior cardinal margin 

 with a long narrow groove, apparently for the reception of a 

 slender projection of the other valve; posterior side beveled 

 from above, edge thin ; ligament external, in a deep cavity ; 

 muscular scars distinct, shallow ; pallial line simple. Fossil. 

 Carboniferous ; Indiana. M. subelliptica, Hall. 



? GONioPHORA, Phillips, 1848. Silur., Devon. ; Eur., N. Am. G. 

 cymbaeforinis, Sowb. U. Silur. ; England. 



CoRALLioPHAGA, Blainv., 1824. 



Syn. — Lithophagella, Gray, 1847. 



Distr. — 5 sp. Mediterranean, in the burrows of the Litho- 

 domus ; sometimes two or three dead shells are found one within 

 the other, besides the original owner of the cell. South Sea. 

 Fossil ; Eocene — . G. coralliophaga, Gmel. (cxiv, 58, 59). 



Shell long, cylindrical, thin, slightly gaping behind ; hinge- 

 teeth 2*2, and a laminar posterior tooth ; pallial line with a wide 

 and shallow sinus. 



Anisodonta, Deshayes, 1860. 



Distr. — 2 sp. I. Bourbon. A. complanatum, Dh. (cxv, 64). 

 Eocene ; Paris Basin. 



Shell transversely elongated, compressed, inequilateral ; hinge 

 thick ; a large conical tooth and a triangular socket in each valve ; 

 ligament external. Anterior adductor scar very small, and 

 comprised between two prominent ribs (one parallel and the 



