112 
PECTUNCULUS brevirostris, 
TAB. CCCCLXXIL- fig. l. 
Spec. Char. Transversely obovate, rather ob- 
lique, and inequilateral, convex, obscurely 
costated, concentrically striated ; hinge 
line rather straight; beaks short, not ob- 
lique ; hinge teeth few. 
There is a slight elevation of the surface along the 
anterior side from the beak to the edge, where it pro- 
duces a gentle projection, and a little below this is the 
greatest length of the shell ; the costrn are convex, but 
so little elevated as to be hardly discoverable in some 
parts: some specimens have elevated lines between 
them, but possibly they are the effect of wear * the teeth 
of the hinge are few, and very oblique ; below the area 
of the ligament, it is more inequilateral, less convex, and 
not so square as P. pulvinatus of Lamarck. 
An abundant and well known shell in the Bognor 
Rocks; I have never observed any variation of conse- 
quence in its form; it wants the heartshaped space 
described by Brocchi in his Area insubrica, and has 
shorter beaks. 
PECTUNCULUS sublsevis. 
TAB. CCCCLXXI1. —fig, 4. 
Spec. Char. Transversely obovate, sequilate- 
ral, rather gibbose, with many slightly 
elevated ribs ; beaks short, nearly close ; 
sides smooth. 
Both the sides of this shell are nearly destitute of ribs; 
there is a depressed space upon the anterior, which 
bounds a convex surface near that extremity of the hinge; 
the large hinge teeth occupy a regular arch below the 
area for the ligament, which area is small; the teeth 
upon the edge of the shell, are small and regular. 
Found in loose yellow sand at Blackdown, where the 
substance of the shell is replaced by Silex. 
