200 On the Relations of Certain 



O. unguis, as figured by Orbigny (Voy., t. 22, f. 1-7). 

 With the form of jaw described by Shuttle worth and the 

 quadrate marginal teeth, it would seem that Simpulopsis 

 belongs to the Helicin(B and not to the Saccinince. It may 

 be noticed that, even form of shell alone considered, some 

 of the species might appropriately be placed near to Bulim- 

 ulus. 



Guppy (Ann. and Mag. Nat. Hist., Jan., 1866) described 

 8. corrugatus,* from Trinidad. Of the animal he says, 

 " mantle edge narrowly reflexed over the peristome." Sub- 

 sequently, the same author (Amer. Jour, of Conch., VI, 308, 

 1871) mentions having ascertained, from a young example 

 of 8. corrugatus, the characters of the dentition of 8impu- 

 lopsis, and that it resembles that of 8uccinea more than he 

 had anticipated. He says, "the odontophore is moderately 

 large, but the individual teeth are very minute and resemble 

 those of 8accinea, particularly, perhaps, 8. ovalis." 



It seems to us that one important characteristic of the 

 dentition of 8uccinea, absent in that of 8impulopsis, is the 

 gap or notch in (as if by the cutting away of) the lower 

 edge of the base of attachment in the central, and corres- 

 ponding gap in the inner edge of the laterals. 



Fischer and Crosse, in 1867, established the genus Xan- 

 thonyx (Jour. Conch., 1867, p. 221, et seq., pi. x, figs. 1-4), 

 describing as the type Vitrina 8amichrasti Brot {I. c, p. 70, 

 pi. iv, fig. 2), and referred to the same genus 8impulopsis 

 8aUeana, 8. Cordovana and (with some doubt) 8. Chia- 

 pensis. 



Among the generic characters of the animal of Xanthonyx^ 

 derived from examination of a specimen of X. 8uinichrasti, 

 communicated by Brot, are the following, " Animal testa 

 sua multo majus, hand omnino inclusum," and *' maxilla 

 arcuata, costata ; tseniola liugualis dentibus basi subquad- 



* Guppy compares his species with S. Brasiliensis (Syn. of S. obtusa Sow.), from 

 which indeed it seems scarcely distinguishable. 



