16 MOLLUSCA. 
b. Last whorl disconnected from the preceding near the aperture. 
3. Choanopoma rigidulum. (Tab. I. fig. 3.) 
Cyclostoma rigidulum, Morelet, Test. Noviss. ii. p. 18°. 
Cistula rigidula, Pfr. Monogr. Pneum. Vivent. ii. p. 184°; Gray, Cat. Phaneropn. p. 191°. 
Adamsiella rigidula, Fischer & Crosse, Miss. Scient. Mex., Mollusca, ii. p. 176, t. 42. fig. 12. 
Hab. N. GuaTeMALA: province of Vera Paz?%, in rocky localities (Morelet 1). 
4, Choanopoma osberti. 
Adamsiella osberti, Tristr. P.Z.S. 1861, p. 232*; Pfr. Monogr. Pneum. Vivent. iii. p. 120°; 
Fischer & Crosse, Miss. Scient. Mex., Mollusca, 11. t. 42. fig. 13 (letterpress not yet 
published). 
Hab. Guatemata (Salvin? 2). 
The operculum is thick, calcareous, with prominent edges of the single whorls. 
The genus Adamsiella has been distinguished by Pfeiffer from Chondropoma by its 
operculum being cartilaginous instead of calcareous; but this difference is effaced by 
gradual transitions. A specimen of C. rigidulum from Patel’s collection, now in the 
Berlin Museum, exhibits a thick calcareous operculum. The majority of Pfeiffer’s 
species of Adamsiella have the last whorl not disconnected from the preceding. 
CHONDROPOMA. 
Chondropoma, Pfeiffer, in Zeitschr. f. Malak. 1847, p. 109. 
Operculum cartilaginous, either throughout or with a thin calcareous layer outside 
(Cistula, Pfr.). Shell conical, ovate or elongate, with varying sculpture, often of a 
reddish colour with brown interrupted bands. 
a. Sculpture vertical only. 
aa. Shell conical. 
1. Chondropoma pleurophorum. 
Cyclostoma pleurophorum, Pfr. P.Z.S. 1851, p. 245'; Martini & Chemnitz, Syst. Conch.-Cab. ed. 2, 
Cyclostoma, no. 299, p. 299, t. 40. figg.5, 6% 
Cistula pleurophora, Pfr. Monogr. Vivent. i. p. 262°; Gray, Cat. Phaneropn. p. 183‘. 
Hab. Honvuras !2324: probably collected by Dyson. 
Very distinct from all the following by the short conical form and the wide angu- 
lated umbilicus. 
2. Chondropoma andrews. (Tab. I. fig. 4.) 
Cyclostoma andrewse, Ancey, in Annales de Malacol. ii. p. 251 (1886) ’. 
Hab. Gulf of Honpuras }. 
