WHITEAVES.] DEVONIAN FOSSILS, MACKENZIE RIVER BASIN. 243 



Maximum diameter, twenty three millimetres; width of umbilicus 

 (as measured on the suture), eight mm. ; longest diameter of aperture, 

 nine mm. 



Mackenzie Eiver, at the " Eamparts," E. G. McConnell, 1888 : one 

 specimen. 



This little shell seems to differ from the Euomplialus inops, E. rudis 

 and E. Hecale of Hall in its depressed spire, and from the E. clymeni- 

 sides of Hall (which is identical with the StraparoUus Canadensis of 

 Bilhngs) in its smaller size, much less slender whorls and consequently 

 narrower umbilicus. 



EUOMI'HALUS 3Iaskusi.* (N. Sp.) 

 Plate 31, tig. 4. 



Shell rather large, discoidal, spire small, periphery flattened convex. 

 Volutions four or live, coiled on nearly the same plane and increasing 

 gradually in size, the inner ones, as seen from above, rounded, with a 

 minute elevated apex, the two outer ones strongly angulated and bear- 

 ing a single row of nodules or tubercles at their outer and upper mar- 

 gin. On the more perfect of the only two specimens collected the 

 characters of the tubercles are shown only on the last volution but 

 one. At its commencement they are quite minute and closely ar- 

 ranged, but, as they increase in size with great regularity, at its outer 

 termination they are about three millimetres and a half in their 

 largest diameter and somewhat quadrangular in outline. Characters 

 of the lowei- or umbilical side and those of the aperture unknown. 

 The only surface markings that happen to be preserved are a minute 

 spiral impressed line in the centre of the nodulous keel bordering the 

 periphery above, and an equally minute spiral raised line on each side 

 of it. 



Hay Eiver, forty miles above its mouth, E. G. McConnell, 1887 : 

 two natural moulds of the exterior of the upper side of the shell. The 

 figure on Plate 31 was drawn from and the foregoing description 

 based on a gutta percha impression of the more perfect of these two 

 moulds. 



The species appears to have been very similar in size and shape to 

 the Euomplialus (or Pleuronotus) DeCewi of Billings, from the Corni- 

 ferous Limestone of Ontario, but in the former tlie outer margin of 

 the last two volutions is tuberculated above and probably was so below. 



* An abbreviation of the Cree name (Maskusikan sipi) for theiHay Kivor. 



