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. Maugerse, which is believed 

 to be a Caribbean species, (not Californian, as stated by 

 Wbodw. 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 

 lip, 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. 1*25, "24, '7. 



The largest specimen must have measured 1*43 : mean div. 60^. 

 Sab. Mazatlan ; not common : L'pool Col. 



Tablet 815 contains 5 sp. slender. 816, 5 do. swollen. 817, 

 5 do. normal state. 818, 5 do. dark variety, approaching A. 

 Maugerse in texture. 819, 2 sp. of distorted growth. 



4- 237. APLEXA ELATA, Gould. 

 Physa e., Gould Col. fy Mex. Shells, p. 6, pi. 14, f. 4. 



It 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 it is 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. Maugerse. 

 Exactly at the suture there is generally an ill-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. 



Hob. 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. 



