356 UNITED STATES GEOLOGICAL SURVEY OF TI3E TERRITORIES. 



2. TEREBRISPIRA, Conrad. * 



Shells of medium size, with spire much produced and canal 

 short; volutions convex, angular, and strongly spirally ridged; plaits 

 of columella not exposed externally; outer lip internally sulcated. — 

 (F. elegans, Emmons.) 

 .5. piestochilus, Meek. 



Shells of small size, with spire and canal produced; volutions 

 flattened or moderately convex and finely spirally striated, sometimes 

 with vertical folds ; plait or plaits of columella not exposed in a direct 

 view into the aperture, very oblique, and occupying a higher position 

 than in either of the foregoing; outer lip smooth within. — (Fusus 

 Scarborough^ Meek and Hayden.) 



4. mesorhytis, Meek. 



Shell agreeing nearly with the last in form, but with plaits of 

 columella stronger, comparatively little oblique, and exposed directly 

 opposite the middle of the aperture; surface with fine spiral striae, 

 and vertical costa?. — (Fasciolaria {Mesorhytis) gracilentis, Meek.) 



5. cryptorhytis, Meek. 



Shells generally under medyim size, with volutions convex, but 

 constricted above, and provided with regular vertical costge or small 

 folds; plaits of columella very oblique, not exposed in a direct view 

 into the aperture, and occupying a higher position than in the typical 

 group; outer lip smooth within. — {Rostellaria fusiformis, Hall and 

 Meek ; not d'Orbigny.) 



The type of the group Piestochilus was originally referred provisionally 

 to the genus Fusus, when only imperfect specimens, merely showing its form 

 and surface-markings, were known. Subsequently, on examining others, I 

 was led to the conclusion that it could not be a true Fusus, and thought, from 

 its general appearance, that it was at least more probably related to Clavel- 

 lithes of Svvaiuson. In removing it doubtfully, however, to the latter genus, 

 I was strongly impressed with the belief that it would at least form the type 



* At the same tiiuo that Mr. Conrad described the subgenus Terebrispira, he proposed another 

 subgenus, Lirosoma, founded ou his Fusus sulcosus, from the Miocene, a pyriform shell, with a much- 

 depressed spire, a ventricose body-volution, a narrow, straight, rather produced canal, and a single loug, 

 very oblique, plait, exposed at the usual position ou the columella. It also has the internally-striated 

 outer lip of Fasciolaria ; but it differs so widely iu form from that genus that I have hardly felt war- 

 ranted in including it as a subgenus under the same. Mr. Conrad has Bince described another species, 

 in which the plait on the columella is obsolete. 



