ANATINIDA. 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.” 
ANATINIDA. 
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, 
Neera, 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. myalis 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 im 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 4. norvegica. We scarcely 
know its use in the animal ceconomy, but presume it is to 
fortify the hinge, by acting lke the check-tape of a trunk to 
prevent too great an opening and strain on it. 
