Some new Upper Greensand Bivalves. 119 



stinctions are its transversely marked posterior ears, the inter- 

 stitial radiations, greater number of ribs, and greater inflation 

 of the left valve (and probably its smaller size). The radiations 

 and posterior ear indicate its affinity with P. Aptiensis ; but the 

 great difference in the number of ribs, their square form, and 

 the imbrications in irregular lines, the substitution of oblique 

 markings on the anterior ear for radiations, and on the posterior 

 ear for close transverse lines, sufficiently distinguish it. With 

 P. Robinaldinus it has some distant affinity. 



Rare. Collected by Mr. Perceval (Trin. Hall), to whom I am 

 indebted for the use of it. University, Mr. Farren. 



Hinnites trilinearis. PI. VI. fig. 2. 

 Shell suborbicular ; one valve flat, the other somewhat convex ; 

 both very thin and irregular. Ornamented with radiating 

 ribs, which are closest on the flat valve. The ribs are orna- 

 mented with three longitudinal lines or keels, of which the 

 middle one is generally the largest, and also with exceedingly 

 close transverse strise, which, from their delicacy, are seldom 

 preserved. On the convex side the ribs number from fifteen 

 to about twenty, and have intervening spaces, more than 

 twice their own width, which are quite smooth. On the flat 

 side are some twenty-five or more ribs, which are slightly 

 smaller than those of the other valve. The cast shows in the 

 intermediate spaces indications of each having had two or 

 three strise. 



Small worn fragments of this species, which are not uncom- 

 mon, may easily be mistaken for Pecten Beaveri, to which the 

 shell, but for its irregular growth, would bear some resemblance. 

 None of the specimens have the umbones perfect, or show trace 

 of an ear. 



Coll. University; J. Carter, Esq.; Mr. Farren, &c. 

 A very marked variety occurs which has good claims to be 

 considered a distinct species. It is distinguished by having all 

 the ribs much closer and higher, and those of the convex side 

 nearly as wide as the intervening spaces ; it also commonly has 

 a striation in each interspace, and as many as five wide folds on 

 each rib. On the flat valve the folds on the ribs are very ob- 

 scure; the interspaces commonly have a single strong striation, 

 and appear to have been finely striated transversely. I have 

 provisionally marked it Hinnites pedinatus. 

 Rare. Coll. University ; J. Carter, Esq. 

 Loc. Cambridge and Ashwell. 



Area (?) mlcata. PI. VI. fig. 3. 

 Oblong, narrow at the posterior end ; very inflated, small. Um- 



