110 PYRAMIDELLID.E. 



given by its founder was sufficient. At all events that 

 name is universally recognized. 



The next question is, what are the limits of this genus ? 

 i. e. do the species furnished with a tooth (whatever may 

 be their sculpture) belong to Odostomia, the ribbed 

 species without a tooth to Turbonilla or Chemnitzia, and 

 the smooth and toothless species to Eulimella ? I can- 

 not admit any such distinction ; nor can I draw a line 

 between Odostomia and Chemnitzia, or between either 

 of them and Eulimella. I have detected the tooth in 

 several so-called species of Chemnitzia, e. g. fenestrata, 

 lactea (or elegantissima) , pusilla, and gracilis; Philippi 

 described his C. densecostata as having the aperture 

 " superne subplicata ; >J and Clark observed in a speci- 

 men of 0. acicula [Eulimella acicula, F. & H.) " a de- 

 cided pillar-fold." This last observation I will confirm. 

 Every naturalist is aware that a generic character which 

 pervades the species taken as a whole may not be pos- 

 sessed by all of them. In the present case there are 

 other characters that serve as ties of union ; and not a 

 single character can be found to distinguish any one of 

 the three supposed genera from its allies. 



The group of shells now under consideration — call it 

 a single genus or a collection of genera — appears to be 

 intimately related to Aclis on one side, and less closely 

 on the other side to Ianthina, which leads through Sti- 

 lifer to Eulima. Montagu suggested the conchological 

 affinity of 0. spiralis and other species to Tornatella (or 

 Actceon) — a view that has been lately advocated by A. 

 Adams, Clark, and Morch on malacological grounds. 

 But that genus has not a retractile proboscis, nor is the 

 apex of its shell either reversed or inverted; and the 

 operculum is constructed on a different plan from that 

 of Odostomia. Their lingual ribands are also very 



