219 



This genus receives Myiilus hirundo, Linn, of which I do not know of 

 any having been found fossil. 



CXLI. Perna. A flat irregular bivalve ; the hinge formed of many 

 parallel linear teeth, not articulating, arranged on a transverse straight 

 line. 



In this genus, formed by Bruguiere, are placed Ostrca perna, O. isogona, 

 O. ephippium, O. picta, and O. legumen. Linn. Here are likewise placed, 

 by Bruguiere, two fossil shells found on the borders of the Rhine. 



Not having the opportunity of seeing the work in which those fossil 

 shells are delineated, BerL Naturf. No. 11. Tab. 9, Fig. 9, I am unable 

 to judge how far they agree with the following shell, which appears to 

 belong to this genus, This shell is figured by M. Walch, Tome n. 

 PL D. v. The substance of the shell, which is very thick, is formed of 

 innumerable thin plates, which are exceedingly brittle, but still possess- 

 ing a considerable portion of the original colour and brilliancy of the 

 nacre. The hinge, which is nearly as wide as the shell itself) is flat, and 

 formed by numerous longitudinal and parallel grooves. 



This shell was first found on the mountain Del Sappo, near Bologna, 

 by Monti; and, since then, a stratum of similar shells has been found in 

 the mountain Audona, in Piedmont, by M. Allion. A representation 

 of this fossil is given Plate XV. Fig. 8, from a specimen which I obtained 

 from Mr. Strange's collection. From a more perfect shell, which was 

 in the Leverian Museum, I conclude that the valve in this fossil has lost 

 about half its length. 



Lamarck, who, we have seen, has followed Bruguiere in separating 

 several new genera from the genus Ostrea of Linnaeus, has added the 

 following new genus, formed from recent shells lately discovered in the 

 Red Sea and in the Antilles. 



CXLIT. Crenatula. An irregularly-formed flat bivalve; closed, not 

 giving passage to any byssus ; the hinge linear, excavated and crenulated 

 by a row of small pits, which receive the ligament. 



