139 



inlets. At Exmouth they are of very large size, often more 

 than 2 inches transverse measure, of a fine ochraceous colour ; 

 the fishermen call them " mud hens." 



This family, according to our views, contains only a single 

 genus, Anatina, long used by authors for this group, but which, 

 without good reason, has been dismembered and split into the 

 genera Lyonsia, Osteodesma, Thracia, Cochleodesma, Periploma, 

 Neaera, and Poromya. We have examined more specimens of 

 the four first so-called genera, than are sufficient to entitle us 

 to say, that the animals of all of them are identical as to 

 essentials of the soft parts, and there is also, in all, the great 

 conchological characteristic, the accessorial testaceous ossicle. 

 I believe that the generic term Anatina has the priority, but 

 it is a matter of indifference if either of the other appellations 

 are applied, so that we have not eight genera for the same 

 animal. All this confusion has arisen from M. Deshayes 

 having, in his comments on Lamarck, shown that he had not 

 observed the animals, by having collected and adopted the 

 artificial genera of authors; what is more remarkable, this 

 eminent zoologist admits that he did not know whether all 

 the species of the tribe were provided with the ossicle, and 

 instances as doubtful the A. myalls of Lamarck, our A. de- 

 clivis. We have not only seen the testaceous accessory of 

 this species, but of every other British Anatina; that ap- 

 pendage is the invariable distinguishing character of this 

 family, which is the only one that is furnished with this 

 curious cardinal internal distinct testaceous addition which 

 clasps the valves, or is imbedded in the cartilage of the 

 apophysary cavity ; its shape is various, usually a semilunar 

 minute cord, sometimes subtrigonal ; it is exceedingly brittle, 

 in appearance at least, except in A. norvegica. We scarcely 

 know its use in the animal oeconomy, but presume it is to 

 fortify the hinge, by acting like the check-tape of a trunk to 

 prevent too great an opening and strain on it. 



