218 PEDICLE. 



known Scallop belongs, contains numerous species, some of which 

 are found in the British Seas. The Hinnites Pusio (P. Pusio of 

 some authors) has been separated on account of the irregularity 

 of the external surface of one valve. Fig. 171 to 173. 

 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, Fig. 174. 



3. Plagiostoma. Unattached, with an area between the urn- 



bones. Fig. 176. 

 4 Dianchora. Attached by the point of the umbo. Fig. 175. 



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



valve, divided by a slit. Fig. 1 77. 



6. Plicatula. Plicated, a very small area in one valve. Fig. 



178. 



PECTINATED. (Pecten, a comb.) Marked in a regular series of 

 ridges. 



PECTUNCULUS. (Pecten, dim.) Fam. Arcacea, Lam. and Bl.— 

 Bescr. Equivalve, sub-equilateral, orbicular, thick, covered with 

 a velvety epidermis, striated longitudinally ; ventral margin den- 

 ticulated 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 ligament ; 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. Fig. 134, P. pilosus. 



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



