522 Mr. G. B. Sowerby on Mtheria ttihifera. 



been adopted by Ocken, and Schweigger ; and Mr. Sowerby in his 

 Genera of Shells, has figured one of the species described by 

 Lamarck, JEtheria semilunata : that which has been brought by 

 M. Caillaud appears to be distinct; it even proves, by its ex- 

 treme variety in form, that the four iEtheriae of Lamarck only 

 constitute two species ; these shells presenting the most singular 

 variations according to the form of the substance to which they 

 have been attached, and being fixed indiscriminately by one or the 

 other valve, which changes the relative position of the ligament 

 and umbones, and renders them dextral or sinistral. Having 

 examined and compared all the known individuals of the species 

 described by M. Lamarck, we have been confirmed in the opinion 

 we had adopted upon seeing such diversified specimens of M. 

 Caillaud's. The names given by Lamarck to these species, being 

 taken from their forms, cannot be preserved. We therefore pro- 

 pose the specific name of (1) JEtheria Lamarckiz^ for the species 

 formed by the combination in one of the ^theriae elliptica and 

 trigonula of Lam. (2) JEtheria Cailliaudt, for that which M. 

 Caillaud has brought from the Nile, and which differs from 

 JEtheria Lamarckii in the colour of its pearl, which is very 

 micaceous and white ; in its less elliptical, more elongated, and 

 often very narrow shape, and in its beak being sometimes several 

 inches long : that of (3) JEtheria plumbea for Lamarck's ^therice 

 semilunata and transversa. 



Some Account of a fourth Species o/^THERIA, by G. B. 

 Sowerby, F. L. S. 



One of the most interesting and valuable of the numerous un- 

 described species of Testaceous MoUusca, which I have purchased 

 in the collection of the venerable George Humphreys, (a celebrated 

 dealer, whose practical knowledge has far exceeded that of any 

 other person in the business), and which I found among Jiis 

 Ostrece Hi/otes, but without any ticket, was this ^Etheria : it is 

 the more interesting as it bears a resemblance to another division 

 of the Ostrea;, from its having the irregular tubular spines, so 

 characteristic of Lamarck's Ostrece Hyotis and imbricata. 



