HELIX-OXYCHONA. 133 



with brown or purplish, marked with irregularly scattered dots 

 which appear translucent by transmitted light ; surface rather 

 smooth, shining, with ill-defined oblique striulre. The spire is short, 

 conoidal ; apex obtuse ; whorls 4-}, convex, separated by moderately 

 impressed sutures, the last sloping above toward the bluntly sub- 

 angular periphery, slightly deflexed at the aperture. The aperture 

 is quite oblique, rounded-subtrigonal, and shows the bands inside ; 

 the lip is white, expanded all around, reflexed and appressed over 

 the umbilicus. Alt. 22, diam. 24 mill. ; alt. 17, diam. 24 mill. 



Central Ame'rica ; Mexico (7) 



H. trigonostoma PFEIFFER, in Philippi, Abbildungen, etc., i, p. 

 154, t. 4, f. 8 (1844) ; Proc. Zool. Soc. Lond. 1845, p. 41 ; Conchyl. 

 Cab., p. 292, t. 49, f. 10 ; Monographia i, p. 229. REEVE, Conch. 

 Icon., f. 584 (1852). CROSSE ET FISCHER, Moll. Mex. et Guat., p. 

 291, 1. 11, f. 6a, b, c, d. (vars. luteo-albida, elevato-conica, intermedia, 

 subunicolor, obscura*) (1878). H. salleana PFEIFFER, Proc. Zool. 

 Soc. Lond., 1849, p. 129 ; Conchyl. Cab., p. 281, t. 124, f. 17, 18 ; 

 Monographia iii, p. 173. REEVE, Conch. Icon., f. 564, b. (" H. 

 lalliana Pf. " TRISTRAM P. Z. S. 1861, p. 230 ?) 



This species is very variable in form, degree of depression and 

 banding. The bands are generally narrow above, broader beneath ; 

 the base is generally one or two banded, the periphery surmounted 

 by a band. The more elevated forms have a longer, more straight 

 and subvertical columella. Crosse and Fischer (loc. cit., supra) rec- 

 ognize a number of varieties based chiefly on color patterns ; judging 

 from the specimens before me, the coloration is not sufficiently 

 stable or constant to admit us to classify the mutations satisfactorily. 

 The form called H. salleana by Pfeiffer is thin, globose, more 

 elevated than typical trigonostoma. It is figured on plate 18, 

 figs. 1, 2. 



H. GUILLARMODT Shuttleworth. PI. 57, figs. 32, 33. 



Imperforate, depressed, about equally convex above and below, 

 keeled at the ]><;. iphery, thin but rather strong, whitish, encircled 

 by deep brown bands, one just above the periphery, one on the base, 

 and sometimes a third narrow one immediately beneath the suture. 

 Surface rather smooth and shining, striatulate and often indented 

 by little pits; spire convex, depressed, not showing bands; apex 

 blunt; whorls 4 to 4*, the first 1* or 2 smooth, the remainder 

 striate; sutures linear, scarcely impressed ; last whorl convex above 



