277 



■aperture elliptical in outline but deeply emarginate by the encroach- 

 xnent of the preceding volution. 



"Surface marked by numerous, closely arranged, small but distinct, 

 though not very prominent, Hexuous, transverse ribs, which bifurcate 

 about the middle of the sides and then pass uninterruptedly over the 

 periphery. 



" The sutural lines are so crowded together and confused that, although 

 fairly well preserved in places, it is scarcely possible to follow the details 

 of any single one. The siphonal saddle, however, is small, a little higher 

 than broad, with a minutely trifurcate apex, and an appressed spur on 

 «ach side below. The first lateral saddle is large, ramose and unequally 

 bipartite or obscurely tripartite at its summit. The siphonal lobe is large 

 and symmetrical, with three branchlets on each side, two of which are 

 lateral and one terminal, but the lowest of the two pairs of lateral branch- 

 lets is much the smallest of the three pairs. 



" The only specimen collected is considsrably eroded near the aperture, 

 as represented in fig. 1, but in the uneroded portion the maximum dia- 

 meter is about forty millimetres, and the greatest breadth fourteen. 



" The writer has much pleasure in associating with this species the 

 name of its discoverer, Mr. James Deans of Victoria, Y. I., who accom- 

 panied Mr. James Richardson in his exploration of the Queen Charlotte 

 Islands, in 1872, and who has since presented some unusually perfect 

 specimens of the fossils of the Cretaceous rocks of those islands to the 

 Museum of the Geological Survey Department at Ottawa. 



" 0. Deansii appears to belong to the small group of Ammonites of 

 which Olcostephanus Astieri is the type, and for which M. Pavlow has 

 recently (1891) proposed the generic or subgeneric name Astieria* Ac- 

 cording to M. Pavlow, the Olcostephani of the group of 0. Astieri form a 

 natural group, a genus (Astieria) if one prefers to consider the Olcoste- 

 phani as a family, or a subgenus if one would rather regard Olcostephanus 

 as a genus. 



" The shape and surface ornamentation of 0. Deansii are very similar 

 to those of 0. Jeannotti. But in 0. Jeannotti the ribs bifurcate at the 

 umbilical margin, and are represejited as so prominent as to everywhere 

 break the general contour if the shell is viewed laterally. The siphonal 

 saddles of 0. Jeannotti, too, are described as broad, and the figures show 

 that they are much broader than high. In 0. Deansii, on the other 

 hand, the ribs bifurcate half way across the sides, at a considerable dis- 

 tance from the umbilical margin, and are not sufficiently prominent to 

 interrupt the continuity of the outline of the shell in a full side view. 



*Bulletin Societe Imperiale des Naturalistes de Moscou, Annee 1891, N. Ser., vol. v. 

 p. 491. 



2^— M. F. 



