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MY'TILUS Antiquorum. 
TAB. CCLXXV.---Figs. 1, 2, and 3. 
Spec. Cuar. Elongated, ovate, rather gibbose, 
smooth, straight; beaks obtuse, nearly close ; 
hinge toothed. 
A  sucrt swelling opposite the hinge renders the two 
sides of the shell more similar than they are in the 
common Muscle; and the general roundness of its 
form also serves to distinguish it; the teeth in the hinge 
close to the beaks are very distinct, they are generally 
four, but vary in number. The length is rather more 
than twice the width. 
I have received this shell from several Friends who 
have found it at Woodbridge, Ipswieh, and in other 
parts of the Suffolk Crag. The most complete suite of 
specimens was lent me by Professor Sedgwick, some of 
which I have figured. The younger individuals possess 
a considerable degree of transparency ; they are all so 
brittle that whole ones are seldom obtained. 
MYTILUS aleformis. 
TAB. CCLXXV.---Fig. 4. 
Spec. Cuar. Obovate, with an acuminated beak, 
curved, depressed, smooth, with teeth in the 
hinge. 
Pur edge is sharp; it forms a very regular curve from 
the pointed beak round to the deeply indented side 
opposite the hinge: there are three teeth under the 
beak. 
