New Species of Fossils. 299 



narrow silt which expands at its outer termination into a 

 narrow and longitudinally elliptical orifice, exactly in a line 

 with the siphuncle, and the branches are similarly narrow 

 divergent slits, each of which widens into a smaller and cir- 

 cular orifice externally. 



Surface markings consisting only, so far as known, of 

 extremely fine transverse striations, which are too minute 

 to be shewn in the figure. 



Sutures slightly concave at the sides, closely approxi- 

 mated but rather nearer together posteriorly than ante- 

 riorly: siphuncle exogastric, marginal and placed in the 

 median line of the venter. 



Approximate dimensions of an average specimen (the one 

 figured): entire length, thirty eight millimetres; length of 

 the septate portion, twenty one mm. ; greatest breadth, 

 twelve mm. 



Grand Eapids of the Saskatchewan below Old Portage, J. 

 B. Tyrrell, 1890: a number of casts of the interior of the 

 shell, in a pale brownish yellow or nearly white dolomitic 

 limestone. 



A singular little species, apparently well characterized 

 by its diminutive size, ovately conical, slender and nearly 

 equilateral contour, as viewed laterally, and by its narrowly 

 contracted and widely divergent Y shaped aperture. It is 

 not at all likely to be mistaken for any American species, 

 and is perhaps most nearly related to the G. clava of Bar- 

 rande, 1 young specimens of which have a very similar mar- 

 ginal outline. The aperture of G. clava, however, is regu- 

 larly T shaped at all stages of growth, and in the adult 

 stage it seems to differ very widely from the present species, 

 both in its dimensions and in its general contour. 



1 SystSine Silurian du Centre de la Boherne, Prague and Paris, vol. ii, 1865 

 pi. 77, figs. 6-22, and pi. 92, figs. 10-13. 



O. clava is from Etage E of Bohemia, which is said to be the equivalent of the 

 Lower Ludlow cf England. 



