THE CYCLOPHORID LAA^^D MOLLUSKS OF AMERICA 143 



The radula of T. gealei has the formula 3:3:3:3. According to 

 Crosse and Fischer the jaw has a median projection, the verge is long 

 and is on the side of the neck behind the tentacles, tapering gradually 

 and bearing a seminal groove. There is no terminal appendage. 



KEY TO THE SPECIES OF TOMOCYCLUS 



Axial sculpture consisting of slender ribs gealei 



Axial sculpture not consisting of slender ribs but of fine incremental 

 lines. 



Outer peristome narrow guatemalensis 



Outer peristome not narrow. 



Siphon strongly developed siphonis 



Siphon not strongly developed. 



Whorls strongly rounded constrictus 



Whorls not strongly rounded. 



Shell large, height more than 35 mm simulacrum 



Shell smaller, length less than 27 mm copanensis 



TOMOCYCLUS GEALEI Crosse and Fischer 



Plate 19, Figure 1 



1872. Tomocyclus gealei Ckosse and Fischer, Journ. Conchyl., vol. 20, p. 77. 

 1886. Tomocyclus gealei Fischer and Crosse, Mission scientifique au Mexique et 



dans I'Am^rique centrale, vol. 2, pt. 7, pp. 118-120, pi. 40, figs. 1-3. 

 1890. Megalomastoma {Tomocyclus) gealei von Martens, Biologia Centrali- 



Americana, p. 10. 



Shell very large, very elongate-turrited, covered by a pale yellowish- 

 brown periostracum, which shows a few axial streaks of darker brown. 

 Peristome bluish white, which is also the color of the interior of the 

 aperture. The early whorls are decollated in all our specimens ; those 

 remaining are appressed at the summit, well rounded, and marked by 

 somewhat sinuous, retractively curved axial riblets, which are about 

 as wide as the spaces that separate them. In addition to this the whorls 

 are marked by very closely spaced spiral striations. Suture strongly 

 impressed. Periphery well rounded. Base moderately long with a 

 strong, heavy, spiral keel bounding the outer edge of the umbilicus, 

 which is open. Aperture circular ; peristome double, the inner slightly 

 exserted; the outer broadly flaringly expanded, with a slit in the 

 parietal wall, which at some little distance behind the edge of the 

 peristome develops into a perforation, the perforation being arched 

 over by the two sides of the peristome, which almost form a siphon. 

 Operculum typically tomocyclid. 



The specimen described and figured, U.S.N.M, No. 321034, bears the 

 label "Central America." It has 7 whorls remaining and measures: 

 Height, 40.7 mm.; greater diameter, 17.8 mm.; lesser diameter, 11.9 

 mm. Height of aperture, 14.1 mm. externally, 7.9 mm. internally; 

 diameter, 13.2 mm. externally, 7.7 mm. internally. 



