146 BULIiETIN 181, UNITEiD STATElS NlAlTIONlAiL MUSlEUM 



The United States National Museum collections contain also the 

 following specimens: 



U.S.N.M. No. 516028, a topotype; U.S.N.M. No. 250693, 4 speci- 

 mens received from Rolle, collected at Finca de Providencia, Guate- 

 mala; U.S.N.M. No. 321030, 1 specimen received from Sowerby and 

 Fulton, labeled "Guatemala." 



This species resembles T. siphonis, but differs from it in its weaker 

 siphonal development and in having the whorls much more strongly 

 rounded and the basal keel much stronger. 



TOMOCYCLUS SIMULACRUM (Morelet) 



Plate 19, Figure 6 



1S49. Cyclostoma simulacrum Mokelet, Testacea novissima insulae Cubanae et 

 Americae centralis, p. 22. 



1852. Megaloma stoma simulacrum Pfeifeeb, Monographia pneumonopomorum 



viventium, vol. 1, p. 131. 



1853. Cyclostoma simulacrum Pfeiffeb, Martini-Chemnitz Conchylien Cabinet, 



vol. 1, sect. 19, p. 267, pi. 36, figs. 11, 12. 

 1864. Megalomastoma simulacrum Soweeby, Thesaurus conchyliorum, vol. 3, 



ul. 263, figs. 3, 4. 

 1872. Tomocyclus simulacrum Ckosse and Fischer, Journ. Conchyl., vol. 20, p. 76. 

 1878. Tomocyclus simulacrum Kobelt, Illustrirtes Conchylienbuch, p. 195, pi. 61, 



fig. 22. 

 1878. Megalomastoma simulacrum Reeve, Conchologia iconica, vol. 20, p. 8, 



fig. 72. 

 1883. Megalomastoma simulacrum Tryon, Manual Conchology, vol. 2, p. 282, pi. 



75, fig. 61. 

 1886. Tomocyclus simulacrum Crosse and Fischer, Mission scientifique an 



Mexique et dans I'Am^rique centrale, vol. 2, pt. 7, pp. 121-124, pi. 40, 



figs. 9, 9a ; pi. 44, figs. 1, la. 



Shell large, covered with a chocolate-brown periostracum, which 

 grows paler toward the tip. Peristome yellowish bluish white, which 

 is also the color of the interior of the aperture. Early whorls decol- 

 lated in all our specimens ; those remaining moderately well rounded, 

 appressed at the summit, and marked by rather irregular incremental 

 lines. Suture strongly constricted. Periphery well rounded. Base 

 with a moderately strong keel marking the outer limit of the um- 

 bilicus. This disappears on the last quarter of the last turn. Aper- 

 ture circular ; peristome double, the inner slightly exserted ; the outer 

 broadly, sinuously flaringly expanded. A slit on the middle of the 

 parietal wall with the two sides reflected over it partly covers a round 

 puncture a little behind the edge of the peristome. 



The specimen figured, U.S.N.M. No. 203656, was received from 

 Bland and comes from Guatemala. It has 5.7 whorls remaining 

 and measures: Height, 38 mm.; greater diameter, 16.6 mm.; lesser 

 diameter, 11.1 mm. Height of aperture externally, 13.4 mm., in- 

 ternally, 6.8 mm. ; diameter externally, 13.4 mm., internally, 6.7 mm. 



