$4 
PECTEN fibrosus. 
TAB. CXXXYI .—Fig. 2. 
Spec. Char. Depressed, orbicular, with a rectan- 
gular beak, nine or ten broadish diverging 
grooves and numerous sharp concentric striae ; 
ears equal, rectangular ; margin undulated 
internally. 
Rather longer than broad ; the back is formed of two 
straight lines meeting at an angle, sometimes greater, but 
seldom less than a right angle ; the undulations within the 
margin are regular and rather deep. The striae are com- 
posed of small very prominent sharp ridges that hold the 
shell firmly to the stone in which it lies. 
This is remarkable at first sight for its broad and few 
sulci, and for the fine undulating transverse striae all over 
them. I have but seldom seen it in pairs, but Mr. 
Strangewayes has a pair from Carrington, Oxfordshire^ 
and I have an excellent specimen from the Chatley Corn- 
brash, by favour of T. Meade ,esq. and a small one showing 
the inside from Oxfordshire. These last two are figured. 
Mr. Mantell was so kind as to send me one from North 
Leach, Gloucestershire, which has only 9 cost®, and 
Mrs. Gent has met with something similar, but plainer at 
Keliaways ; if these should prove to be distinct specie^ 
I shall notice them again. 
