ANOMIA. 323 



The parts which seem, at first glance, in each to be iden- 

 tical, prove not to be homologous, upon investigation. 



Atiomia has really very close relations with Pecten, and 

 is connected to the latter by the curious genus Hemipecten of 

 Reeve. The perforation in one of the valves of Anomia., 

 is chiefly a greater extension of the auricular sinus in 

 Pecten ; and when the very 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 be- 

 coming attached, eventually becomes detached with a part 

 of the adductor muscle, and forms the opercular process. 

 The animal is deleterious, and has a peppery taste. 



The species of this genus are distributed through the 

 seas of all regions, and fossil forms range far back in time, 

 but never appear to have been very abundant. There is 

 great difficulty in the determination of both recent and 

 fossil forms. Opinion as to the true sources of specific 

 character among the Anomi(s has fluctuated greatly ; some 

 conchologists would limit the number of admitted forms to 

 a very few ; others would swell the specific list by num- 

 bers of too evident varieties. 



In the following account of the British Anomia, we have 

 adopted the views at present held by many of the most 

 distinguished malacologists of this country and of the Con- 

 tinent. We do so, however, only provisionally, and regret 

 that the subdivisions here adopted are not borne out by 

 an examination into the characters of the several animals. 

 To this subject Mr. Clark has this year addressed his 

 particular attention : the results of bis researches go 

 strongly against the notion of the specific permanency of 

 characters in our native Anoinia, and we feel bound to give 

 the following extract from his communication relative to 



