180 MAZATLAN UNIVALVES 
This fine species, which is generally named P. Peruviana in 
collections, is quite distinct from the types in the Br. Mus. It 
much more nearly approaches A. Maugere, which is believed 
to be a Caribbean species, (not Californian, as stated by 
Woodw. Man. ii.171.) It differs in shape, which is never so 
elongated, and in colour which is almost always orange horn, 
with a tendency to darker shades, in rays, below the suture. 
Shell swollen, thin, glossy, with an extremely thin columellar 
hip, projecting beyond the aperture, and indented at the base 
of the body whirl. The length of the spire varies in different 
specimens, as does also the amount of convexity. The true 
A. Peruviana has a very prominent apex, with shouldered, 
swollen body whirl. Allowance must be made in the following 
measurements for the constant erosion of the apex. A slender 
specimen measures long. 1°23, long. spir. °27, lat. °63. 
A swollen sp. il 2os SOAe eer Wades 
The largest specimen must have measured 1°43: mean div. 60°. 
Hab.—Mazatlan ; not common: L’pool Col. 
Tablet 815 cortains 5 sp. slender.—816, 5 do. swollen.—817, 
5 do. normal state.—818, 5 do. dark variety, approaching A. 
Maugere in texture.—819, 2 sp. of distorted growth. 
237. APLEXA ELATA, Gould. 
Physa e., Gould Cal. §& Mex. Shells, p. 6, pl. 14, f.(. 
Tt is almost impossible to draw the line between this species 
and the young of A. aurantia. Nevertheless, as a vast number 
of this shell were sent, and very few of the other, it is presumed 
that itis adult. It differs considerably from the adult form of 
A. aurantia, being very much smaller, thinner, more pointed, 
of a light horn colour, with the whirls extremely smooth, and 
the apex never eroded. In shape it is more like A. Maugere. 
Exactly at the suture there is generally an ili-defined line of 
lighter colour with one of darker colour below. It varies 
somewhat, like the last species, in the comparative length, of 
the spire. An unusually large specimen measures long. 1°08, 
long. spir. °28, lat. °5, mean div. 50°. 
Hab.—Lower California, Major Rich.—Mazatlan ; very com- 
mon; L’ pool Col. 
Tablet 820 contains 10 sp. normal state.—821, 6 do. more 
swollen.—822, 9 do. colour approaching A. aurantia.—823, a 
distorted sp. slightly angled at the suture. 
