59 



characters of two genera not hitherto reckoned very closely allied, Pecten 

 and Anomia. They appeared to be varieties of one and the same species, 

 although on being submitted to Dr. Carpenter for microscopic examina- 

 tion, he detected a rudimental sculpturing over the whole of the visible 

 external surface of one of them which is wanting in the other. In form 

 and general outline, and in the structure of the hinge, Hemipecten, as the 

 name given to this shell denotes, resembles the preceding genus ; but in 

 substance, and in its habit of being affixed to its place of attachment by the 

 flat valve, it resembles Anomia ; and a consideration of this affinity has led 

 to the observance by Professor Forbes of relations of more physiological 

 import.* From the circumstance of the lower valve being perforated by a 

 deep sinus, of which there is no corresponding growth in the upper, it 

 might be compared with Pedum; but in that genus, which lives imbedded 

 in madrepore, the habits of the animal are different, and the shell has an 

 umbonal area, like that of Spondylus. 



The two specimens (now in the collection of T. Lombe Taylor, Esq.) 

 were obtained from a coral and stony bottom at the depth of about four- 

 teen fathoms. The under valve of each is smooth, showing it to have been 

 affixed, the upper valve, covered, in part, in both specimens with particles 

 of coral and parasitic shells, is in one smooth and colourless, in the other 

 decussately wrinkled and delicately rayed with orange-red. 



Species. 

 1. Forbesianus, Adams 8f Reeve. 



(Figured in the Mollusca of the Voyage of the Samarang, PI. 20.) 



Genus 6. LIMA, Bruguiere. 



Animal ; oval ; mantle freely open, its margins pendent and 

 fringed ivith long tentacular filaments ; ocelli absent or incon- 

 spicuous ; no siphons ; body produced, in part linguiform ; foot 

 small, Ungulate, furnished toith a byssal groove ; labial palps 

 subtriangular , small, pectinated ; mouth surrounded by tenta- 



* "Anomia has really very close relations with Pecten, and is connected to the latter by the 

 curious genus Hemipecten of Reeve. The perforation iu one of the valves of Anomia is chiefly 

 a greater extension of the auricular sinus in Pecten, and when the young fry of this genus shall 

 have been carefully observed, we believe they will be found spinning a byssus which, passing 

 through this sinus, fixes the shell in the first instance, before a portion of it becoming attached, 

 eventually becomes detached with a part of the adductor muscle, and forms the opercular pro- 

 cess." — Forbes and Eanley, Brit. Moll., vol. ii. p. 323. 



