DRYM^EUS. 183 



BulimulidcB was impossible ; and in the absence of this, the facts of 

 geographic distribution could not be developed, and speculation 

 upon the past history of the group was at a stand still. 



The discovery that a finely, regularly latticed apex is correllated 

 with the special form of teeth and jaw of the genus, liberates the 

 systematist and the theorist. The main features of the internal 

 anatomy of any Bulimuloid snail may now be predicted with a very 

 great degree of certainty from an examination of the earliest whorls 

 of the shell. 



Drymceus is very closely related to the genera Oxychonaand Neo- 

 petrceus; but the former of these has conchological characteristics 

 which most conchologists will probably agree render its retention 

 as a separate genus advisable, and in Neopetrceus the peculiar denti- 

 tion and somewhat diverse apical sculpture are characters deserving 

 recognition in nomenclature, and likely to be lost sight of if the 

 group be merged into Drymceus. It is an early branch, which 

 diverged from Drymceus near the origin of the latter from the Ortho- 

 tomous Bulimuli, and with a specialized radula, still retains in large 

 measure, the early pattern of nepionic sculpture. 



My selection of the generic name Drymceus Alb., 1850, for this 

 group instead of the name Otostomus Beck, 1837, used by von Mar- 

 tens since 1873, was a necessary consequence of the facts developed 

 by examination into the history of the latter name. These facts 

 have been briefly set forth in the preceding volume of this work (pp. 

 95, last paragraph, and 107); but as errors in nomenclature are 

 hard to eradicate, they may bear repetition. 



Otostomus was proposed by Beck in 1837 for the species B. sig- 

 natus, myotis, lateratis, lagotis andnavicula. Gray and Hermannsen, 

 in or about 1847, selected B. signatus as the type of the group. H. 

 & A. Adams, in 1855, used Otostomus in a generic sense, excluding 

 signatus from the group, but including most of the forms of Zap lag- 

 ins and Drymceus s. s., with numerous incongruous species. Von 

 Martens, in 1860, mentions B. aurisleporis as the type. 



It is universally admitted that when the author of a genus selects 

 no type, one may be selected by the next author concerning himself 

 with the group. In this case, both Gray and Hermannsen named 

 B. signatus as the type ; Gray in a paper written expressly for the 

 purpose of indicating the types of molluscan genera, Herrmannsen in 

 one of the most widely used works of his generation. The subse- 

 quent selection of another species, B. aurisleporis, as type of Otoatomus 



