^HITEAVES.] LARAMIE AND CRETACEOUS IXVERTEBRATA. 53 



Surface marked by transverse and nearly straight ribs, which in- 

 crease in number either by bifurcation or intercalation, especially in 

 half grown and very young shells, so that there are often twice or 

 perhaps three times as many on the centre of the periphery as on tlie 

 umbilical margin. In specimens which measure about two inches in their 

 greatest diameter and in still smaller ones, there is a row of distantly 

 arranged small nodes on each side near the periphery of the outer volu- 

 tion and a faint tendency towards the same kind of sculpture around 

 the umbilical margin. In the largest specimens, however, these rows 

 of nodes are entirely obsolete. Septation, as far as it can be made out, 

 apparently very like that of Scaphites nodosus. 



Bast Branch of the Poplar River, on the 40th Parallel, (the locality 

 where the Wood Mountain xVstronomical Station was established) (t. 

 M. Dawson, ISt-i, H. M. North Amej-ican Boundary Commission : one 

 large but rather imperfect specimen. Old Wives Creek, Township 10, 

 Eange 11, west of 3rd Principal Mei-idian, E. Ci. McConnell, 1884 : one 

 large and nearly j)erfect specimen and several others varying from less 

 than one inch to two inches in their greatest diameter. 



The characters which are most relied upon for the separation of this 

 species from S. nodosus, Owen, are the much greater size of the former 

 and its more nearly globose form. The septation of both of these 

 forms, indeed, appears to be much alike, and very young shells of S. 

 .subglohosus have a somewhat similar sculpture to S. Conradi, but in 

 large individuals of the former the ribbed surface of the outer volution 

 is entirely free from nodes. 



Placenticeras placenta, Dekay. (Sp.) 



Ainmonites phicrnta, Dekay. 1S28. Ann. X. Y. Lye. Nat Hist., vol. ii., p. 27S, 

 pi. 5, fi;;, 2 (3 by mistake).— Morton. 1829. Journ. Ac. Nat. 

 Sc. Phil., vol. VI., p. 195 ; and Am. Journ. Sc. and Arts, 

 vol. XVIIL, pi. 2, figs. 1, 2 and 3 ; also, 1S:54, Synops. Org. 

 llem. Cret. Form. U. S., p. 36. pi. 2, figs. 1 and 2. 



Placenticeras pi o.crnti I, Meek. 1S7(;. Rep. V. S. Geol. Surv. Terr., vol. IX., p. 4i;o, 

 pi. 24, figs. 2a, b. 



South Branch of the Saskatchewan, Prof H, Toule Hind, 1858. 

 White Mud Elver, (or Frenchman's Creek) on the 49th Parallel, G. M. 

 Dawson, 1874, H. M. North American Boundary Commission : one 

 large and characteristic fragment. Blood Indian Creek, longitude 111° 

 west, Prof J. Macoun, 1879 : one largo si^ecimen and two or three 

 fragments. St. Mary Elver, near its mouth, (i. M. Dawson, 18S] ; one 

 specimen which measures upwards of seventeen inches in diameter, 



