PECTINID^. ^ 291 



vei*}^ characteristic, and so is also the small marginal cartilage- 

 pit. 



HiNNiTES, Defrance, 1821. 



Distr. — 4 sp. Europe, California, etc. Fossil; Triassic — . H. 

 sinuosus, Lam. (cxxxiii, 22, 23). 



Shell oval, irregular, inequivalve, subequilateral, close, 

 adhering b}' the right valve ; eared irregularly ; hinge without 

 teeth ; ligament thiciv, in a deep, narrow pit. 



Differs from Pecten in its irregular growth, and in being 

 adherent. 



AvicuLOPECTEN, M'Coy, 1852. 



Syn. — ? Aphania, de Koninck. 



Distr. — Fossil. Devonian — Carb. ; Spitzbergen — Australia, 

 N. America. A. granosin^, Sowb. (cxxxii, 5). 



Shell inequivalve, suborbicular, eared ; hinge-areas flat, with 

 several long, narrow cartilage-furrows, slightly oblique on each 

 side of tlie umbones ; right valve with a deep and narrow byssal 

 sinus beneath the anterior ear; adductor impression large, 

 simple, subcentral ; pedal scar small and deep, beneath the 

 umbo. 



Aviculopecten does not possess the prismatic structure of the 

 Aviculidae, but the peculiar corrugated tubular structure of the 

 Pectinidse (Meek^ It bears the same relations to existing Pec- 

 tens as Pterinea does to existing Aviculas. 



PTERiNOPECTEN, Hall, 1883. Hinge-line long; wings not well- 

 defined, being simple expansions or extensions of the upper 

 lateral margins to the hinge-line. 5 sp. Hamilton and Chemung 

 Groups ; New York. A. undosus. Hall. 



EUCHONDRiA, Mcck, 1874. Uncharacterized. Type, Aviculo- 

 pecten ni'glectui', M. and W. (cxxxii, 7, 8). Carboniferous; Ills. 



LYRIOPEOTEN, Hall, 1883. Differs from Aviculopecten in the 

 short hinge-line and very small anterior wing ; surface usually 

 ornamented with strong rays. 5 sp. Chemung and Hamilton 

 Groups ; New York, A. magnijicus, Hall. 



Pernopecten, Winchell, 1865. 



Etym. — Perna and Pecten^ from a combination of some of the 

 characters of the two genera. Syn. — Entolium, Meek, 1865. 



Distr. — Fossil, 1 sp. Carboniferous ; Michigan, Belgium, 

 Nassau. P. gr/a&er. Hall (cxxxii, 6). Probably others referred 

 to Avicula, Pterinea, and more especially to Aviculopecten, 

 Amussium and Pecten. 



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. 



