HELICELLA. 247 



plenty of writers quite willing to do this. Xerophila has been used 

 in Ornithology (P. Z. S. 1840, p. 175) but later in date than Held's 

 publication. 



The division of the genus into sections is difficult on account of 

 the large number of species intermediate in form ; and the data at 

 hand are insufficient for their discrimination on anatomical grounds. 

 It is further complicated by the number of names proposed for mem- 

 bers of the group, and their intricate synonymy. Although per- 

 haps fairly able to distinguish small systematic groups, the writer 

 claims to be no expert in perceiving the subtle distinctions made by 

 some authors in this genus. Those who find a greater number of 

 sections useful should avoid two radical faults in the present Euro- 

 pean usage: i. e. the use of preoccupied names and the use of old 

 names for groups containing none of the species on which such sec- 

 tional terms were originally based. Monterosato has recently pro- 

 posed an entire new set of no less than forty-one sectional names, 

 which for uniformity all begin with Xero-. There is much dry 

 humor in this proposition, for he ignores all previous sectional 

 nomenclature except Xeroleuca, and the new terms are mostly 

 Greek X Latin hybrids, hideous in etymology and senseless in mean- 

 ing. 



f Xerocrassa Monts. Jacosta Gray. 



Subgenus HELICELLA, | Heliomanes Moq. Xeroleuca Kob. 

 penis retractor mus- j Helicella s. str. Obelus Hartm. 



cle present and well j Xerocampyltea Kob. Trochula Schliiter. 

 developed. j Candidula Kob. Cochlicella Risso. 



^Mouilearia Mouss. 



Subgenus THEBA, no f 



penis-retractor mus- | Theba Risso. 

 cle. Muscus glands <j Lejeania Ancey. 

 present. No dart | Platytheba Pils. 

 in the empty sack. ^ 



Section Xerocrassa Monterosato, 1892. 



Xerocrassa MONTS., Moll. Terr. Is. adiacenti Sicil., p. 23, type H. 

 seetzeni. 



Shell narrowly umbilicated, thick solid and chalky, varying from 

 discoidal to turbinate. Type H. seetzeni. 



A desert form of Heliomanes characteristic of Palestine and 

 Arabia, perhaps worth a sectional name. 



