84 HOLOSPIRA. 



apical whorls rounded, a little projecting, nipple-like. The 

 last whorl is rounded below, and not produced forward, 

 though the peristome is usually free. Aperture subcircular, 

 vertical, peristome continuous, expanded and slightly re- 

 flected, rarely adnate above. The internal axis (fig. 57) is 

 about one-fifth the diam. of shell, pillar-like, of about equal 

 diameter above and below. It is encircled by a slight ridge 

 or convexity, which revolves below the middle in each whorl, 

 throughout the cylindrical portion of the shell, though weak 

 in the intermediate whorls. In the penultimate whorl a 

 callous cord is superposed upon this ridge, producing an 

 obtuse lamella about one whorl long, extending into the last 

 whorl but not reaching the aperture. The pillar is other- 

 wise smooth, showing some fine longitudinal white lines on a 

 bluish-white ground. 



Length 13, diam. 4.2 mm.; whorls 14%. 



Length 11%, diam. 4.4 mm. ; whorls- 12%. 



Length 13%, diam. 4.5 mm.; whorls 15 (Pfr. type). 



Length 10. diam. 3.8 mm.; whorls 1214. 



Length 9.7, diam. 4 mm. ; whorls 11%. 



Pueblo, (Pfr.) : Mat amor as Izucar, in the State of Puebla, 

 on cactus (Boucard). 



Cylindrella tryoni PFR., Journ de Conchyl., xv, 1867, p. 

 438; Novit. Conch., p. 433, pi. 97, f. 5-7; Monogr., vi, p. 390; 

 viii, 447. Holospira tryoni Pfr., C. & F., Journ de Conch., 

 1870, pp. 14, 24, pi. 5, f. 5 (jaw) ; Miss. Scient. Mex., Moll., 

 i, p. 331, pi. 17, f. 6; with var. appressa. v. MARTENS, Bio- 

 logia, p. 276. Bostrichocentrum tryoni Pfr., STREBEL, Bei- 

 trag, iv, p. 81, pi. 5, f. 3; pi. 14, f. 13, 16 A, B. ? Holospira 

 gealei H. Ad., FISCH. & CROSSE, Miss. Scient., Moll., i, p. 333, 

 pi. 17, f. 7. CROSSE, J. de C., xl, 1892, p. 271, pi. 5, f. 2.- 

 H. tryoni CROSSE, Journ. de Conch., xl, 1892, p. 267, pi. 5, 

 f. 5, 5 a. 



A very compactly coiled shell, with narrow whorls. It 

 varies from a quite cylindrical contour to one in which the 

 shell is slightly wider above than below. The supposed 

 variety appressa is merely an individual variation, the peri- 

 stome being adnate above, as in my fig. 56. The series be- 



