332 CONTRIBUTIONS TO CANADIAN PALiEONTOLODY. 



than high, broadest above the niidheight, slightly produced and rather 

 narro\\ly njunded at the base : aperture apparently not far from circular. 



The only surface markings that happen to be preserved consist of rather 

 closely disposed, flexuous and oblique stri;e of growth. 



Dimensions of the most perfect specimen collected : entire height, as 

 measured from a horizontal line drawn on the same level as tlie apex, to 

 the centre of the base, twenty-four millimetres : greatest height of the 

 outer volution twenty-two mm. . maximum bi-eadth of the same, twenty- 

 five mm. 



Pentamerus Point, Lake Manitoba, J. B. Tyrrell and J. F. Whiteaves, 

 188.S : three specimens, in each of which most of the test is exfoliated, 

 only a few small fragments of its outer surface Ijeing preserved. 



This shell has ii, much narrower and smaller spire than the P. lineatum 

 of Conrad, the diminished size of the sjiire in the former being obviously 

 due to the greater amount of overlap in the outer volutions. 



(S.) Naticopsis Manitobensis. (N. Sp.) 



Plate ib, tig. 7. 



Shell imperforate, turbiniform, subglobose, a little higher than broad : 

 spire elevated, occupying at least one-fourth, and in some specimens 

 nearly one-third, of the entire height. Volutions about four, convex, regu- 

 larly rounded and increasing rather rapidly in size, the outer one large 

 and ventricose : aperture suVjovate : outer lip thin and simple. 



Surface markings consisting of numerous, regularly and closely dis- 

 posed, Ijut very slightly elevated, minute raised lines, or faint and 

 crowded, narrow, thread-like plications, which are too small to be seen 

 without the use of a lens, and which cross the volutions obliquely. 



As the nuclear volution is broken off in each of the specimens collected, 

 it is impossible to give very accurate measurements of any of them, but 

 the one figured is represented as twice the natural size, and the largest 

 specimen upon which any of the characteristic surface ornamentation is 

 preserved was probably nearly or quite eighteen millimetres in height 

 when perfect. 



Lake Manitoba, at Pentamerus Point (eleven specimens), and Monroe 

 Point (two specimens) ; J. B. Tyrrell and J. F. Whiteaves, 1888. 



It is doubtful whether this species and the next should be referred to 

 NaticopHia or Naliai. The opercula of both of these species are unknown, 

 and there is no evidence that the columellar lip of either was flattened or 

 transversely striated, as in NafAcopsis, but in the most perfect specimens of 

 both, the aperture is filled with the matrix and the columella almost com- 

 pletely covered. Deshayes and others have maintained that the genus 



