232 PECTEW. 



PATELLIFOEM. {Patella, a dish ; forma, shape.) Shaped like 



a dish, or like shells of the genus Patella. 

 PATELLOIDA. Quoy and Gaimard. Lottia, Gray. — Fam, 

 Phyllidiana, Lam. — Descr. Patelliform, rather flat ; apex obtuse, 

 leaning towards the posterior margin ; musciilar impression not 

 symmetrical, but widest on the right side near the head of the 

 animal ; central disc of a variable brown colour. On rocks and 

 sea- weeds in aU climates. — Obs. The shells of this genus so 

 closely resemble patella that it is almost impossible to make 

 the distinction from the shells alone. They are, however, gene- 

 rally flatter, and have the apex placed somewhat nearer the 

 posterior margin. The animals are very distinct. P. Antil- 

 larum, PL xii. fig. 231, 

 PATELLOIDEA, Bl. or patelliform shells. The third family of 

 the order Monopleurobranchiata, Bl. ; the animals of which are 

 described as depressed, flattened, covered by a wide external 

 shell, which is patelliform and non- symmetrical. This family 

 contains the genera Umbrella and Siphonaria. 

 PATE0CLE8. Montf. A genus of microscopic Foraminifera. 

 PALULAEIA. Sw. A sub-genus of " Anodontinse," Sw. thus 

 described : " Shell nearly equilateral, round or cordate j no teeth, 

 P. ovata, Sw." Ex. Conch, pi. 36, rotundatus, lb. pi. 137. 

 PAVONIA. D'Orb. A genus of microscopic Poraminifera. 

 PAXTODON. Schum. Htbia, Lam. 



PECTEN. Brug. {A comb.) Fam. Pectenides, Lam. Subostra- 

 cea, BL — Descr. Inequivalve, ribbed longitudinally, nearly equi- 

 lateral, with a triangular auricle on each side of the umbones ; 

 hinge linear, destitute of teeth, having a central pit containing 

 the cartilage ; muscular impressions one on each valve, large, 

 subcentral. — Ob^. This genus of beautiful shells, to which the 

 well known ScaUop 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 

 irregxilarity of the external surface of one valve. The Mono- 

 graph of this -genus in Thesaurus Conchyliorum, by the author, 

 contains 101 species. Plates 12 to 20. Pig. 171 to 173. PL x. 



