GASTROPODA. l"-'i 



floUplrm.) 



mis SOLENOSI'Ii: A. ii. gen. 



Smtrma (part.) of SALTKK and KII.I.INOS. 

 Mvrckitonia (part.) ' WHITKIKLD and other author*. 



1'or -fii'-ri.- li.ir.u-ters see page 



This is a long-lived group of species that can always be recognized by the broad 

 saliently margined concave band which occupies the greater part of the middle 

 third of the whorls. In their general appearance they remind one of Ttirritellidct 

 r.ither than pleurotomaroids, and so far as we can see there is no serious objection 

 to considering them as the ancestors of that graceful family of shells. 



So far as known the notch or sinus in the outer lip was never prolonged into 

 a slit. This of itself is a suspicious circumstance when we consider the usual 

 progress of development pertaining to nearly all of the various types of the 

 Pleurotomariida: The proportionally great width of the band, together with the 

 fact that its transverse markings are of the same character as the tine recurved 

 hues of growth indeed they are mere connecting continuations of them strength- 

 ens this suspicion almost to conviction that Solenospira represents the root of a line 

 of development that later on (in Carboniferous and subsequent times) diverged 

 widely from ordinary pleurotomarians. And what family is a more likely continu- 

 ation of the line than the Turritellithel 



We place the genus with the Pleurotomariida, in the immediate vicinity of 

 Hormotoma, chiefly because we know of no other stock from which it might have 

 been derived. The depth of the apertural sinus and the fact that its deepest part is 

 marked off in such a manner that with continued growth of the shell it formed a 

 sharply margined spiral band, are both highly characteristic conditions of the 

 rifiirotoinnriiiln; while the features mentioned in the preceding paragraph are such 

 only as might very well have occurred in the separation of a line culminating in 

 ZWrrMb. 



The oldest of the species which we place here is the Eunema prisca Billings of 

 the Calciferous formation of Canada. An apparently undistinguishable form, 

 occurring in the Stones Kiver group in Minnesota, Wisconsin, Illinois and Tennessee, 

 i- described and figured in this work. The Quebec group furnishes two other 

 spacijs, IfwrdUMMd nd>-linn and M. missisquoi of Billings. The latter of these two 

 species possibly may, when better known, prove to have other affinities. In tlie 

 Black River group we have the type of the genus, Eunema ? pagoda Salter. We 

 know of no other good representatives of the genus, in American deposits, at 

 any rate, until we reach the Hamilton group, from which Hall has described one as 

 ia turricula, or as it is now known. M. micula, the specific name having 



