232 

 Gryphaea — continued. 



plicatida. .o\£d, oblique, underneath slight oblong folds, hook 



lateral . . Mons, 

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



Ostrea. 



Valves plaited, margin dentated. 

 seri'a . . suborbicular, sinister, gigantic, thick ; teeth of the mar- 

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

 diluv i ana. .suhorhicnla.!', right, teeth acutangulate .. 3 inches.. 



Mons. 

 ^o6e/!Z«m. .flabellatedly ovate ; long, subdivided, convex folds, 



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

 jlabelloides . . 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. 

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



bowed ; with longitudinal rugose folds, one beak pro- 

 duced. . Grignon. 

 pectinata. . 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. 

 can«a/a. .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. .oh]ong, narrow, reduced toward the apex, plaits 



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



..Mons. 

 Zarva. .oblong, curved, plicated on the sides; rows of plicse 



unequal; margins crenated. .Maestricht. 

 pennaria . . oh\ong, subarcuate, plicated in two rows; plicee of 



the sides oblique, curved. .Champagne. 

 6i/ro«s. .ovato-rotund ; upper valve convex, smooth; lower 



longitudinally plicated ; margin crenated. .Grignon. 

 Mwda^a. .ovato-oblong, thick, obsoletely plicated, plic?e undate, 



imbricato-squamous ; one beak produced. .Bourdeaux. 

 Valves not plicated. 

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



channelled, striated transversely ; apex rather hooked. 

 lonyirostris . .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. 



