232 

 Gryphaea continued. 



plicatula. .oval, oblique, underneath slight oblong folds, hook 



lateral . . Mons, 

 silicea. .oval, oblique ; no folds ; hook lateral. .Rochefort. 



Ostrea. 



Valves plaited, margin dentated. 



serra. . suborbicular, sinister, gigantic, thick; teeth of the mar- 

 gin large, erect, acutangulate. ,6| inches wide. 

 diluviana.. suborbicular, right, teeth acutangulate. .3 inches. . 



Mons. 

 /a6eWttm..nabellatedly ovate; long, subdivided, convex folds, 



obsoletely squamous ; bowed on each side. .2^ inches. 

 flabelloides. . subtrigonal, thickly plaited ; plaits large, with 



sharp backs, subimbricated ; oblique at the sides. 

 placunata. . semicircular, flat and plaited on both sides ; with 



squamous plaits, divaricating to the sides. 

 flabellula. . oblong, wedge-form, rounded upwards, rather 



bowed; with longitudinal rugose folds, one beak pro- 

 duced. . Grignon. 

 pectlnata. . oblong, bowed, pectinated in folds, valves convex, 



margin serrated, with a middle groove. . 3 or 4 inches. 

 phyllidiana. . oblong, thick ; back convex, with subimbricated 



plaits on both sides. . 4 inches. . Angers. 

 leporina. . oblong, bowed, thick ; disks convex, carinated ; two 



rows of plaits ; outer margin prominently rounded. . 4j 



inches. 

 carinata. .oblong, upper and under valve rather acute; sides 



flat, bowed ; valves complicated, backs carinated, with 



transverse plaits. 

 colubrina. . oblong, narrow, bowed, plaited ; valves semicom- 



plicated, outer side convex. 

 scolopendra. .oblong, narrow, reduced toward the apex, plaits 



in two rows ; oblique, becoming gradually shorter. . If inch 



. .Mons. 

 larva . . oblong, curved, plicated on the sides ; rows of plicae 



unequal; margins crenated. . Maestricht. 

 pennaria. .oblong, subarcuate, plicated in two rows; plicae of 



the sides oblique, curved. .Champagne. 

 bifrons. .ovato- rotund ; upper valve convex, smooth; lower 



longitudinally plicated ; margin crenated. .Grignon. 

 undata. .ovato-oblong, thick, obsoletely plicated, plicae undate, 



imbricato-squamous ; one beak produced. .Bourdeaux. 

 Valves not plicated. 

 crassissima. .elongate, very thick, ponderous ; beak long, wide, 



channelled, striated transversely ; apex rather hooked. 

 longirostris . .lower valve thick, subcucullated ; beak very long, 



contorted. . Sceaux. 

 canalis. .ovato-oblong, very thick ; lower valve with prominent 



beak, channelled, with a flat margin on each side.. 



5 inches. 



