174 MOLLUSCA— CLASS II. BRACHIOPODA. 



formed ; if, on the contrary, they are found upon the radiated valve of a 

 Pecten, they are ribbed accordingly ; and if confined between the spines 

 of an Echinus, they become compressed. This may probably arise from 

 the fact of the Anomiae not being provided with any foot or organ of loco- 

 motion ; they are indeed said to live and die in the same place where they 

 are deposited in ovo. 



The shell of Anomia may be described as being inequivalve, irregular, 

 and fixed. The lower valve, which is generally rather flat, is orbicularly 

 perforated near the hinge ; and the aperture, with the edges turned back, 

 is filled up by the calcareous organ of adhesion ; it is, however, still free 

 within the aperture, and differs in this respect from that of Placunanomia. 

 The upper valve is generally concave, and exhibits the impressions of two 

 accessory cartilages in addition to that of the chief muscle. The ligament 

 is interna], situated beneath the umbones. 



The species which we have selected as an example is common to our 

 own coast. 



Example. 



PL CXXIV. Fig. 1,2 and 3. 



Anomia ephippium, Linnaeus, Syst. Nat., p. 1 150. Lamarck, Anim. sans 

 vert., new edit., vol. vii. p. 273. Enc. Meth., pi. 170. f. 6 and 7. 



Class II. BRACHIOPODA. 



Animal ovatum vel oblongum in testa bivalvi perpetud affixum ; ore 

 mediano ; capite oculisque nullis ; brachiis ciliatis duobus ad spi- 

 ram pertinentibus ; musculis plurimis. Viscera abdominalia parva, 

 lobis pallii utrinque protecta. Branchiae vasculares, symmetrica;, 

 pallii textura mollicella exorientes. 



