ARC A. ARK. 11 
lower angle, which is the reverse in A. Nose : it is also en¬ 
tirely destitute of the zigzag diagonal brown markings : 
length half an inch ; breadth an inch. 
West of England, and Scotland : rare. v. v. 
9. Area minuta. Minute Ark. 
Walker , f.8\—Dorset Cat. pi. 1. f. 16. 
Arcacaudata. Donovan, pi. /S. 
Shell oblong, much produced at one end which is angular 
sloping and truncate, the other end rounded, finely Striate 
transversely, with three or four strong concentric ridges : A 
•beaks small, turning a littleto the longer side, with a smooth - 
canty between them: teeth in a curved line, separated 
by a hollow; length hardly three lines 5 breadth about 
four. 
Sandwich, Scotland, West of Ireland: rare. v. on . 
10. Area rostrata. Elongated Ark . 
Montagu, pi. 2J. f. 7* 
Shell somewhat oval, the smaller end sloping and elon¬ 
gated into a lip which is turned up, the other rounded, 
wrought with extremely, fine regular slightly reflected 
transverse ridges, which are angularly turned across a few 
slight longitudinal ribs from the beaks to the smaller end : 
beaks small, nearly central, almost close together : teeth in 
a curved line, angular, numerous on each side the beak, and 
separated- by a hollow: color pale horny, glossy, some¬ 
times covered with a greenish skin, inside semitraus parent 
and finely polished : length half an inchj breadth three 
quarters. 
St. Abb’s Head, Scotland : very rare. 
11. Area tenuis. Thin Ark . 
Montagu, pi. 29. f. 1. 
Shell somewhat heart-shaped, produced on one side and 
rounded at the margin, white or covered with an olive 
skin: beaks small, not central, slightly inflected towards 
the shorter side; inside smooth, white, and somewhat per- 
laceous; the margin thin: hinge with about fifteen teeth 
placed in a curved line within the margin, six on one side 
and nine on the other, divided by a small concave plate pro¬ 
jecting 
< c5>: 
