FAMILY TURBONILLID^. 



Shell minute, white, slender, elongated, many-whorled, usually 

 longitudinally or spirally sculptured ; columella without plica- 

 tions or with a single small fold ; apex sinistral. 



Animal as in Pyramidellidjo. Operculum corneous, pauci- 

 spiral. 



The species are very small, and mostly more slender than in 

 Pyramidellidne ; they are numerous, and have been separated 

 into a number of inferior groups, which are, for the most part, 

 poorly defined so that their classification is difficult and uncer- 

 tain. As most of these groups are founded on European 

 species, I have not, as a rule, included any extra-limital forms, 

 preferring for my purposes a geographical division of the 

 species. Hitherto the species have neither been monographed 

 nor catalogued. 



Synopsis of Genera. 



Genus TURBONILLA, Risso, 1826. 



Shell slender, elongated, many whorled, generally costulate, 

 apex sinistral, columella vertical, not plicate. Operculum horny, 

 subspiral,the columellar margin entire, face with a spiral groove. 



Animal with wide tentacles, mentum elongated, flattened, 

 usually bilobed in front ; foot large, anteriorly auriculated. 



Comprises a great number of small, graceful, usually white 

 shells ; distribution universal. Fossil, tertiary. The synonyms 

 are Chemnilzia, d'Orb., 1839, not 1850; Pyrgiscus, Philippi, 

 1841 ; Orthostelis, Aradas. 



Section TRAGULA, Monts., 1884. 



Sculpture fenestrate ; spire elevated, acute, apex twisted; 

 whorls scalariform ; columella without fold or tooth. T. 



FENESTRATA, Forbes. 



Section TRABECULA, Monts., 1884. 



Whorls rounded, longitudinally lamellose ; aperture semicir- 

 cular, with an exterior rib ; no apparent spiral sculpture ; apex 



(317) 



