74 MOLLUSCA FROM THE GREAT OOLITE. 



ligamental area is elongated, smooth, and lanceolate, its margins are not in contact, but 

 have between them a distinct elongated aperture, which is beneath the cushion of the 

 ligament. It occurs very frequently in a crushed or imperfect condition, a circumstance 

 which seems to indicate that it was not habitually a mud living species. 



It is met with somewhat rarely throughout the shelly beds of the Great Oolite, and 

 likewise in the middle division of the Inferior OoUte in Gloucestershire. 



Compared with U. glohosum, Ag., it is more elongated, depressed, and oblique ; as the 

 test is always preserved, and the valves disunited, we are precluded from examining the 

 characters of the internal casts. 



Localities. Minchinhampton and Bisley Commons in the Great Oolite ; Leckampton 

 and Selsley HiUs in the Inferior Oolite. 



Unicardium parvulum. Tab. VIII, fig. 6, 6«. 



Testa parvd subdepressd, ovato-ohlongd ; umhonihus subanticis acuminatis, latere antico 

 brevi, postico elongato ; basi curvatd, lined cardinis horizontali, subrectd ; superficie sub- 

 compresso plicis concentricis irregularibus. 



Shell small, rather depressed, ovately oblong ; umbones anterior and acute, anterior 

 side short, posterior side elongated, base curved elliptically ; hinge border lengthened, 

 horizontal, and straight; surface somewhat compressed with irregular concentric pli- 

 cations. 



This httle species has less convexity, and is more oblong than is usual with this genus ; 

 the hinge border is nearly horizontal, but rounded at its extremity, and the valves do not 

 gape perceptibly at the ligamental area ; in many specimens there is an obscurely defined 

 angle directed from the umbo to the antero-ventral border, and in common with other species 

 there is much variation in the degree of obliquity and convexity. One of our specimens, 

 a portion of which exposes the internal cast, has a very fine radiating striae, of which there 

 is no trace upon the external surface of the shell. It occurs not uncommonly in the shelly 

 beds of the Great Oohte, and has also been recognised in the upper portion of the 

 formation. 



Height, 7 lines ; length, 9 lines. 



Locality. Minchinhampton Common. 



Cypricardia. Lam. 1801. 



Gen. Char. Shell equivalve, inequilateral, obhque, transverse, anterior side short ; 

 hinge with two or three cardinal teeth in each valve, and one lateral tooth. Muscular 

 impressions two in each valve ; ligament external. 



