158 PSEUDOCERATITES OF THE CRETACEOUS. 
shell casts they described had acute venters, but this is probably an error. 
In studying this group of fossils such a mistake is easily made, owing to the 
simplicity of the sutures, the narrowness of the flattened venters, and smooth- 
ness and symmetrical aspect of the fossils, although considerably worn and 
altered by abrasion. 
_ The presence of three distinct lines of nodes, the flatness and nodose 
edges of the venter throughout the earlier and ephebic stages, the broad and 
often zigzag outline of the venter in the gerontic stage, caused by the extra 
development of the outer line of alternating nodes, enable one to separate the 
species of this genus readily from those of Metengonoceras, notwithstanding 
the close similarity of the sutures. The young during the neanic stage are 
compressed, involute, and smooth, with concave venter and form like Pro- 
tengonoceras. Von Buch and Neumayr both describe the principal saddles 
of Engonoceras pierdenale as bifid, and this occurs in the species here sup- 
posed to represent Engonoceras, but does not occur, so far as known, in 
Metengonoceras. All specimens so far seen have been casts, either entirely 
naked or with only the nacreous layer partly preserved. 
The attention of collectors is called to the fact that some of the species 
bear no convincing marks of having been autochthonous members of the 
faunas in which they are habitually found. 
This genus differs from Neolobites onky in having denticulated lobes, if 
the figures of the sutures heretofore given correctly represent their outlines. 
_ ENGONOCERAS BELVIDERENSE (Cragin). 
Pl. XVII, figs. 4, 5. 
Ammonites belviderensis Cragin, 1894, 1895, Am. Geol., Vol. XIV, pl. 1, figs. 3-5; 
Vol. XVI, p. 369. i 
Buchiceras (Sphenodiscus) belwiderense Cragin, 1900, Colorado Coll. Studies, Vol. 
VIL, p. 27. 
Through the kindness of Professor Cragin I have seen some specimens 
of this species, and one of these has been given in the figure. This alone 
was not much crushed, but the sutures could not be made out. The aspect 
is similar to that of Eng. uddeni, but the sides and venter are flatter and 
smoother. There are similar nodes on the umbilical shoulders and those on 
the edges are alternate; there are nascent folds on the outer part of the 
sides. It reaches a larger size than other forms before it begins to acquire 
