PECTEN. 



GENERIC CHARACTEn. 



Shell free, bivalve, inequivaive, thin, auriculated, equila- 

 teral j hinge margin tninsverse, rectilinear, connected 

 throughout by a ligament, the cartilage being interior, fix« 

 ed in a triangular fosset of each valve under the apex,' 

 apices contiguous, not elevated ; muscular impression 

 large, subccntral ; palleal impression without sinus: ani 

 m«/suborbicular ; foot very small, sometimes with a bys«= 

 sus ; mantle fringed with tentacular papill£e, of which the 

 series is interrupted somewhat regularly by shorter cylin' 

 drical processes terminating in oculiform disks ; mouth 

 large, transverse, surrounded with fringed lobes, and with 

 a thin lamellated palp on each side ; anus free ; branchiae 

 large. 



OBSERVATIONS. 



The numerous species of shells which form this very 

 beautiful and natural genus, inhabit, almost universally 

 the margins of the marine portion of the globe, from the 

 torrid zone to the inhospitable shores of the Polar seas. 

 Attracted by the regularity of their furm and the beauty 

 of their colouring the ancients distinguished them as ,t 

 group from all other shells. Aristotle and Pliny indica- 

 ted several species, and compared them to a comb or pec- 

 ten from the similitude of their ornamental rib-formed 



PI. 56. 



