ANOMIA 



TESTA inaequivalvis, irregularis; valva inferior 

 prope cardinem perforata, operculo vel appen- 

 did osseae affixa; parietibus aperturae reflexis: 

 impressio muscularis unica, sub centralis, orbicu- 

 laris. Valva altera i^npressionihus muscularibus 



. itribus, approximatis, majore. Ligamen-^ 



'-J turn internum, transversum, sub umbone po- 



■ ' situm. 



When the characters we have described above are atten- 

 tively considered, we think this Genus is in no danger of 

 being confounded with Terehratula, Placuna, or any 

 other Genus with which Linneans, even to the present 

 day unite it. 



The manner in which it is attached^ the peculiarities 

 of its hinge, and its muscular impressions eminently 

 distinguish it, and separate it from all other shells. The 

 Anomia Ephippium, Linn., may be considered as the 

 type of this Genus of inequivalve and irregular shells, 

 which is commonly found attached to rocks, shells, sea 

 weeds, &c. by a bony appendage or operculum with a 

 dilated base, and which is in fact only a continuation of 

 the internal or abductor muscle of the animal ossified 

 at its external extremity, and passing through a perfora- 

 tion or nearly orbicular sinus in the flatter or lower valve : 

 the edges of this perforation are turned back, and it is 

 completely closed by this bony appendage. In the lower 

 valve there is a single, orbicular, nearly central muscular 

 impression, but in the upper or concave valve there are 

 three placed close to each other; of these, that nearest 

 the base of the shell is the largest, and it is connected by 



