344 MOLLUSCA. 
p. 27, t. 2. figg. 1 f,g, t. 10. fig. 7 (embryonal whorl), A-G (anat.), t. 9. figg. 14 (radula 
and 21 (jaw) *. 
Hab. E. Mexico: San Antonio del Monte, between Jalapa and Misantla (Strebel) ; 
Cordova (Sallé 1°). 
3. Xanthonyx sumichrasti. 
Vitrina sumichrasti, Brot, Journ. de Conch. xv. p. 70, t. 4. fig. 2 (1867) *; Monogr. Helic. Vivent. 
v. p. 20°. 
Xanthonyx sumichrasti (Brot), Crosse & Fisch. Journ. de Conch. xv. p. 214, t. 10. figg. 1-4 (sub 
Leptonyx) (jaw, radula, anat.)°; Miss. Scient. Mex., Mollusca, i. p. 201, t. 9. figg. 14-17 
(anat.) *. 
Hab. Mexico, without nearer indication of locality (Sumichrast }~*). 
4, Xanthonyx chiapensis. 
Simpulopsis chiapensis, Pfr. P. Z. 8. 1856, p. 8777; Malak. Blatt. in. p. 230 (1856) *; Monogr. 
Helic. Vivent. iv. p. 802°; Reeve, Conch. Icon. xiii., Simpulopsis, t. 1. fig. 1 *, 
Xanthonyzx chiapensis (Pfr.), Fisch. & Crosse, Miss. Scient. Mex., Mollusca, i. p. 203 °, 
Hab. 8.E. Mexico: Chiapas ((Ghiesbreght 1~*). 
It is probable that these four so-called species are not really distinct. ‘The descrip- 
tions given by Pfeiffer appear to be sufficiently characteristic, but when the figures are 
consulted it is not easy to understand the differences. Fischer and Crosse state that 
spiral strie are also visible in their specimen of X. cordovanus ; Strebel introduces the 
distinct costulation of the first whorl as an important difference between X. cordovanus 
and X. salleanus, but as neither Pfeiffer nor Fischer and Crosse mention it, it remains 
doubtful whether their X. cordovanus is really the X. cordovanus of Strebel. I am 
inclined to agree with the French authors that the four forms may be due to age and 
individual development. 
CRYPTOSTRACON. 
Cryptostrakon, Binney, Ann. N. York Acad. Sci. i. p. 258 (1879). 
Shell vitrinoid, depressed, ear-shaped, with very wide aperture, membranaceous, 
entirely concealed by the mantle. Jaw arched, with a few stout ribs. Radula with 
quadrate irregularly bicuspid marginal teeth. 
Confined to Costa Rica. 
1. Cryptostracon gabbi. 
Cryptostrakon gabbi, Binney, Ann. N. York Acad. Sci. i. pp. 259, 260, t. 11. figg. H-K (living 
animal, shell, jaw, and radula) * (1879) ; i. p. 104, t. 7. fig. K (radula), t. 16. fig. L (jaw) 
(1884) *. 
Shell flat, of about 2 whorls, very membranous, about 14 millim. in greatest diameter. Animal varying from 
black to shades of brown and variously mottled with black or dark brown, about 70 millim. long. 
Hab. Cuntrau Costa Rica: flanks of the Pico Blanco, 5000 to 7000 feet (Gadd 2). 
