OXYSTTLA, MEXICO, ETC. 117 



Beitr. Mex. Land- und Siissw.-Conch. v. p. 34, form A, 4, form B, C, 

 pi. 3, f. 7b, 7c, 4a, b. Ortalichus obductus v. MARTENS, Biol. Centr. 

 Anier., pp. 181, 187 (exclusive of South American references and 

 localities). 



This is so like the Venezuelan 0. obducta that it has deceived 

 a number of excellent conchologists, as may be seen by the above 

 references. Under the lens, one at once sees strong sculptural 

 peculiarities, deccptor having a comparatively coarse pattern of spiral 

 threads, very irregularly waved, and modified by fine malleation, 

 over the entire surface of the last whorl ; while in obducta the 

 spirals are very much finer, usually obsolete or nearly so over a 

 great part of the surface, and in place of the malleation, which is 

 wanting, there are distinct wrinkles along the growth-lines. O. 

 princeps var. trifracta is to come extent a transition form to true 

 princeps. 



It is further distinguished from 0. obducta by the general color- 

 tone and pattern of the last, and especially of the earlier whorls ; a 

 comparison of thirty specimens from numerous Central American 

 and Venezuelan localities showing these features to be constantly 

 different. The long, straight columella is like that of O. obducta. 



Figures 19 and 23 of pi. 24 were drawn from specimens from Pol- 

 von, Nicaragua, the type locality. Fig. 24 is from Nicaragua. Fig. 



20 is a very pale, partially albino specimen from Honduras. Figs. 



21 and 22 represent a very aberrant shell, collected by Prof. Ralph 

 Tate in Nicaragua, exact locality not known ; on a white ground, it 

 is blotched with purplish-black and has three interrupted bands of 

 tawny brown. The long, straight columella causes me to refer it to 

 deceptor rather than toferussaci. 



Another aberrant shell is shown in fig. 25. It is from Panama, 

 and differs from all the preceding by its elongate spire with the whole 

 first whorl black, the striping conspicuous throughout, columella 

 strongly convex, and aperture small. The sculpture is typical. This 

 may be called form perlonya. Alt. 50, diam. 27^, longest axis of 

 aperture 25^ mill. 



The following west Mexican forms, elegans and colimensis, are 

 known only by brief differential diagnoses, insufficient to establish 

 their specific distinction, though they may be valid species. 



0. elegans (Rolle). 



Shell very similar to 0. princeps, but differing in the more slender 



