AD 
MYA ? literata. 
TAB. CCXXIV.---Fig. 1. 
Parkinson, Vol. 3, p. 196, ¢: XITTI, f. 16. 
Descriptive Catal. of Minerals and Fossil Organie 
Pei of Scarborough, &c. p. 129, t. I, 
Srec. Cuar. Transversely oval; subequilateral, 
convex, smooth, thin, with obtuse angularly 
bent ridges upon the central part ; angles of 
the ridges in a longitudinal direction. 
ee eit 
Tue ridges constitute a peculiar feature of this and 
the two following shells ; and at the same time that they 
distinguish the tribe from any other that we know, their 
variations serve as distinctions among themselves. In 
this species their angles are placed in a directly longi- 
tudinal series; they disappear at the sides, and are 
soonest lost upon the anterior: near the beaks the 
angles of several ridges are cut off by short straight 
lines. The shell is thin, and so much broken, that its 
general form is but imperfectly displayed. 
The specimen here represented was sent me by some 
friend from Whitby ; whether it was collected at Malton, 
or not, I do not know: in the Catalogue of Scarborough 
Fossils it is mentioned as being found at the latter place 
m grey Limestone, as this specimen is. It is not possi- 
ble, from the firmness of the stone in which all the 
individuals of this tender family have been protected, 
to disclose the structure of the hinge, and consequently 
to determine with precision what genus to refer them to, 
Among recent shells we know, of nothing analogous, ex- 
cept Mya (Unio) corrugata, which is a strong and 
differently formed shell, that will materially assist us ; 
but as they somewhat resemble the thinner species of the 
genus Mya, they are placed under it, until chance may 
discover characters at present concealed. 
