1896.] NATURAL SCIENCES OF PHILADELPHIA. 15 



NEW SPECIES OF THE HELICOID GENUS POLYGYRA. 

 BY HENRY A. PILSBRY. 



At the request of Mr. John Ponsonby of London, the determina- 

 tion of a series of Polygyras of unknown or doubtful specific 

 identity, from his collection, was undertaken by the writer. In the 

 course of this work, the Mexican species of the genus were reviewed, 

 the identification of the Academy's material verified, and several 

 specific forms, hitherto nameless or under incorrect names, were 

 studied. 



The following communication relates to species of that character- 

 istic " Lower Sonoran " group of Polygyra, of which P. plagioglossa 

 and P. ventrosula represent approximately the extremes in the 

 cycle of form changes. 



The types of P. latispira, matermontana and eiighjpta' are in the 

 collection of the Academy. The types of P. Ponsonbyi are in the 

 same collection and that of Mr. Ponsonby ; and the type of P. 

 albicostulata is in Ponsonby's collection. 



These five species, with P. Mearnsii and P. chiricahuana Dall 

 (Proc. U. S. Nat. Mus., 1895), and P. solidens and P. triangularis 

 Mabille (Bull. Soc. Philomath, de Paris, 1895) complete the list of 

 Polygyras given in the Guide to the Study of Helices, pp. 73, 74. 



P. latispira n. sp. PI. Ill, figs. 13, 14, 15, 16. 



Shell depressed, with convex spire, rounded but noticeably shoul- 

 dered periphery and convex base; unibilicated, the umbilicus 

 within deep and cylindrical, about "8 mm. diam., at the last whorl 

 rapidly enlarging, 2"3 mm. diam., or contained about five times in 

 the diameter of the shell, conspicuously grooved inside. Surface 

 very closely and regularly rib-striate, moderately shining. Light 

 yellow or buff" in color. Whorls 52, closely coiled, slowly widening, 

 rather convex, having an oblique impression behind the outer, and 

 an excavation behind the basal lip. Suture well impressed, descend- 

 ing only a trifle at the aperture. 



Aperture quite oblique, roundly lunate, the lip forming two-thirds 

 of a circle, rather narrowly reflexed ; outer lip bearing an inwardly 

 projecting pointed tooth ; basal lip with a slightly keeled face along 



