PEDICLE. 233 



PECTENIDES. Lam. A family belonging to the second section 

 of the order Conchifera Dimyaria, Lam. including the following 

 genera : 



1. Pecten. Unattached, including Decatopecten and Hin- 



nites. Fig. 171, 172, 173. 



2. Lima. Unattached, gaping. Pig. 174. 



3. Plagiostoma. Unattached, with an area between the 



umbones. Pig. 176. 



4. DiANCHOEA. Attached by the point of the umbo. Pig. 



175. 



5. Spondtlus. Attached, irregular, a triangular area in one 



valve, divided by a slit. Pig. 177. 



6. PiiiCATTJLA. Plicated, a very small area in one valve. 



Pig. 178. 



PECTINATED. {Pecten, a comb.) Marked in a regular series 

 of ridges. 



PECTUNCULUS. {Pecten, dim.) Fam. Arcacea, Lam. and 

 Bl. — Descr. Equivalve, sub- equilateral, orbicular, thick, covered 

 with a velvety epidermis, striated longitudinally ; ventral margin 

 denticidated within ; hinge semi-circular, with a series of small 

 teeth on each side of the umbones, which are separated by a 

 small triangular disc in each valve bearing the Kgament ; mus- 

 cular impressions two in each valve, strongly marked, united by 

 an entire palleal impression. — Obs. Linnsean conchologists have 

 mixed this genus with Area, from which it is, however, totally 

 distinct, not only in the roundness of the general form, but also, 

 and principally, in the curve of the hinge line ; in fact the cha- 

 racters of this genus are so strongly marked that there is no 

 danger of confounding it with any other. It does not contain 

 many species ; two or three are British. The fossil species 

 occur in. London Clay and Calcaire-grossier. The Monograph 

 by Mr. E.eeve contains nineteen species. The generic name, 

 AxiNEA of PoH, claims the priority. Pectunculus pilosus. PI. 

 vii. fig. 134. 



PEDICLE or PEDUNCLE. (Pedunculus, a little foot.) The 

 stem or organ of attachment of the class of shells called in the 



