CONCHIFERA. 



Pernopecten, Winchell, I860. 



Derivation, Perna and Pecten, from a combination of some of 

 the characters of the two genera. 



Type, Aviculopecten limseformis, "White and "Whitfield. 



Shell subequivalve, inequilateral, auriculated; hinge line 

 straight, with a central triangular cartilage pit and a transverse 

 plate, with smaller lateral cartilage pits diminishing in size and 

 depth from the centre outwards. 



Pernopecten agrees with Amusium in its subsymmctrical ears. 

 cardinal cartilage pit, and in the absence of radiating ridges, 

 but differs in its straight hinge line and lateral cartilage pits. 



Fossil, 7 species. Carboniferous limestone. Michigan, Bel- 

 gium, Nassau. Probably others referred to Avicula, Pterinea, 

 and more especially to Aviculopecten, Amusium, and Pecten. 



Aviculopecten (p. 417) does not possess the prismatic of the 

 Aviculidce*, but the peculiar corrugated tubular structure of the 

 Pectinidce (Meek). It bears the same relations to existing 

 Pectens as Pterinea does to existing Aviculas. 



PLlCATtTLA (see p. 414). 



Sub-genus, Harpax (Parkinson, 1811), Deslongchamps, 1858. 



Example, Harpax Parkinsoni, Brown. 



Hinge of attached valve consisting of a flattened triangular 

 plate, traversed by a central more or less perpendicular liga- 

 mental furrow, exterior to which are slightly marked diverging 

 sulci to receive the elevated borders of the ligamental groove 

 in the other valve; the outer borders of the plate form length- 

 ened and elevated dental processes. Hinge plate of free valve 

 traversed mesially by the ligamental groove, the borders to 

 which are elevated and but slightly diverging ; exterior to 

 these are strongly impressed grooves to receive the dental pro- 

 cesses of the other valve. 



Fossil, 16 species. Lias and Lower Oolites. France and 

 England. 



Terqttemia, Tate, 1867. 



Dedicated to M. 0. Terquem, an eminent palaaontologist. 



Example, T. Heberti, Terquem, Mem. Soc. Geol. de Pr., vol. 

 viii. p. 106, t. 13, f. 1—3, 1865. 



Synonym, Carpenteria, E. Deslongchamps, 1858 (non Gray. 

 1856. 



Shell inequivalve, subequilateral, attached by the umbonal 

 portion of the right valve; the left valve slightly concave, 



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