17 
AVICULA lanceolata. 
TAB. DXII.—^g*. 1. 
Spec. Char. Transversely linear-lanceolate, com- 
pressed ; posterior wing large, obtuse-angled ; 
anterior wing minute, pointed. 
Six times as wide as long, very flat ; the beaks are very 
near the anterior extremity ; the posterior extremity is 
narrow and blunt ; the posterior wing extends about one 
third the width of the shell : it is in no part distinct, but 
runs along the superior edge ; its two edges, one of which 
is a continuation of the hinge line, meet at a very obtuse 
angle. 
A very remarkably formed shell (if in fact it be a shell) 
strongly resembling the external bony appendages to 
the abdominal fins of several fishes : the manner in which 
the pair is displayed strongly favours this resemblance, 
and is by no means common among fossil shells. 
Figured from a specimen in the cabinet of H. T. De 
la Beche, Esq., who found it in the Blue-Lyas ofLyme 
Regis, Dorsetshire. 
The shell is imposed upon a plate consisting of per- 
pendicular fibres, of grey carbonate of lime, imbedded 
between the laminae of the slaty clay that composes a 
great part of the Lyas stratum. It is accompanied by a 
small Pecten. 
