HELIX-THELIDOMUS. 65 



The affinities of this form are with H. auricoma on one hand and 

 on the other with (1) the series of trinitaria, barracoensis and 

 laraellicosta ; and (2) that of guantanainensis, proboscidea, rangel- 

 ina. 



The body-whorl is more depressed than in H. auricoma, less full 

 or gibbous below ; the color is lighter than most specimens of auri- 

 coma, but this is a trifling character ; the body-whorl is decidedly 

 more dilated transversely than in auricoma, and the aperture is more 

 oblique. Measuring inside the peristome, the mouth of auricoma 

 is generally higher than wide ; whilst that of bayamensis usually is 

 wider than high. H. guantanamensis is still more depressed and 

 dilated transversely than this species, is rather more finely striate 

 above, and less glabrous beneath, for the stria3 do not become 

 obsolete at the periphery, but extend upon the base. The columella 

 is not truncate in H. bayamensis, as it is in H. rangelina, H. guanta- 

 namensis, etc.; and there is no streak of orange-russet behind the 

 periphery as there is in the last-named species. 



The variation in size is so great that one is almost inclined to say 

 that the species is composed of elements more dissimilar to each 

 other than to allied forms. 



VAKIETY. (PL 17, fig. 44.) The figure represents a large, rather 

 thin-shelled form, regularly and rather finely costulate above ; the 

 aperture is subangular at base, as it almost always is in this species, 

 although not represented sufficiently so in fig. 1 of pi. 2. The 

 largest specimen I have seen measures ; alt. 25, diam. maj. 43, min. 

 33 mill. 



VARIETY. (PI. 1, figs. 15-17.) The form here figured is much 

 smaller than the type, with more oblique, smaller aperture ; above it is 

 strongly costulate-striate, beneath shining, nearly smooth ; whorls 

 about 3? ; aperture truncate oval ; peristome quite thick. Alt. 14, 

 diam. maj. 25, min. 19 mill. A specimen before me measures but 21 

 mill. diam. 



H. GUANTANAMENSIS Poey. PI. 2, figs. 7-9. 



Imperforate, depressed, rather solid, slightly shining, straw-colored 

 or light russet ; regularly obliquely costulate-striate, the sculpture 

 becoming obsolete in the center of the base ; spire a little more 

 depressed than in H. bayamensis, and whorls somewhat less convex 

 above, the last slopingly flattened on the upper surface and some- 

 what so beneath, much dilated transversely, suddenly deeply de- 

 flected to the aperture, and tinged with orange-russet just behind 



5 HELICID^E. 



