114 PSEUDOCERATITES OF THE CRETACEOUS. 
MANTELLICERAS MANTELLI (Sowerby). 
Ammonites mantelli Sowerby, 1814, Min. Conch., pl. 55. 
Ammonites mantelli Sharpe (pars.), 1856, Foss. Moll. of Chalk of England, pl. 18, 
figs. 6, 7 (not fig. 4). 
Ammonites mantelli Schliiter, 1872, Paleontogr., Vol. X XI, pl. 5 (not pl. 6). 
The compressed form, with broad venter, and presenting clearly three 
facets, with four rows of tubercles, more or less well defined, is obviously 
the shell that more uearly than others answers to Sowerby’s description and 
figures. This is obviously the form that in the young is the least involute 
and has the most decidedly quadragonal volutions, becoming compressed in 
later stages. This is the var. (a) of Sharpe, as quoted above. 
MANTELLICERAS COoULONI (d’Orbigny). 
Ammonites mantelli VOrbigny, 1840, Terr. Crétacé, pl. 104 (not pl. 103). 
Ammonites couloni VOrbigny, 1850, Prodrome de Paléontologie, II, p. 147. 
Ammonites mantelli Sharpe, 1856, Foss. Moll. of Chalk of England, pl. 18, fig. 4 (not 
figs. 6, 7). 
Ammonites mantelli Schliiter, 1872, Paleeontogr., Vol. X XI, pl. 6 (not pl. 5). 
This is a highly compressed shell, separable even in the neanic stage 
from mantelli. Thé young are much more compressed than in mantelli, sides 
flatter, and the form resembling that of the full grown of that species when 
the shell is not over three-fourths of an inch, or about 18 mm., in diameter. 
The tubercles are present, but much less prominent in the young than in 
mantelli at the same age. 
MANTELLICERAS PICTETI n. sp. Hyatt. 
Ammonites mantellé Pictet et Campiche, 1859, Terr. Crét. de St. Croix, p. 200, pl. 26. 
The neanic stage, with its more compressed form, but otherwise like 
the young of mantelli, and all stages are finely illustrated by the authors 
quoted above. The volutions are more compressed than in mantelli and 
somewhat less involute in all stages later than the neanic, and the venter 
narrower. The octotuberculate stage is more prolonged and the umbilicus 
wider than in M. couloni. In extreme old age the tubercles are all lost and 
costee are prominent where they cross the narrow rounded venter. There 
are a number of this species and casts of some of Pictet’s originals in the 
Museum of Comparative Zoology. 
