322 OSTREAD^. 



ANOMIA. LiNNJEUfs. 



Shell oblong or suborbicular, usually more or less irregu- 

 lar, inequivalve, surface of upper and convex valve smooth, 

 or lamellar, or ornamented by radiating and scaly striae ; 

 under- valve flattened, deeply emarginated near the beak 

 on one side by a large and ovate or round sinus, through 

 which passes a strong adductor attached to an opercular 

 shelly mass, by which the animal and its shell is fixed to 

 various substances. Beaks very small ; no teeth ; valves 

 united by a short and thick cardinal ligament ; muscular 

 impressions several. 



Animal shaped like the shell, mantle freely open, with 

 pendant margins bearing a double fringe of short cirrhi. 

 No conspicuous ocelli. No siphonal tubes. Body massive. 

 Foot very small, often nearly obsolete. Adductor muscle 

 divided into three portions, the longest passing through the 

 notch in the lower valve, and attached to the opercular 

 piece, partly attached to the inner surfaces of the shell. 

 Branchial leaflets doubled on themselves. Mouth sur- 

 rounded by membranous borders, and two pair of long 

 labial tentacles, striated on both sides. Sexes distinct. 



Linnajus included in his genus Anomia, the species of 

 Terehratula. Misled by a false analogy, he considered 

 these very different mollusks to be organized on the same 

 plan, and the perforations of one of the valves in each to be 

 of similar origin. Lamarck, in like manner, fancied that 

 in Anomia he saw a passage into Terehratula and the 

 Brachiopods ; and some anatomists even believed that they 

 had discovered transitional characters. A close examina- 

 tion shows that there is no relationship of affinity between 

 them, but only a resemblance through formal analogy. 



