32 PSEUDOCERATITES OF THE CRETACEOUS. 
The oldest sutures are very much changed, and look like those of a 
distinct species, but are obviously in the gerontic stage. The bases of the 
saddles are nearer together, the entire parts of the sides much elongated, 
and the lobes longer and narrower and the digitations situated at their 
apical ends much deeper. The saddles are longer and broader, with entire 
bulging sides, and the marginals not increased in number, but much longer 
and larger. 
The sutures have at this stage close similarity to the peculiar outlines 
attributed to Ammonites syriacus by von Buch (fig. 1 of pl. 7 in his Uber 
Ceratiten), but the first lateral is not so broad and does not have the minute 
phylliform marginals of that figure. The marginals on the first lateral 
saddles, and also in the first lateral lobe, are tongue shaped. 
The fourth and fifth lateral saddles are entire, tongue shaped, and 
divided by a narrow bifid lobe. The young sutures, until a late neanic 
stage, have outlines similar to those of some species of 7%ssotia. After this 
the outer saddles become completely denticulated, and again, as described 
above, lose a considerable part of these denticles in old age. 
Fragments of the shell were present on the largest cast. None of the 
specimens was incrusted by any extraneous growths that could be shown 
to have fastened themselves on the surfaces of the casts. 
The figure of the young in an early ephebic substage (PI. I, fig. 12) is 
a very near approach to the old specimen which was crushed on one side 
(PL. I, fig. 10), but of course, owing to differences of age, the nodes are 
larger. There are fifteen nodes on the ventral border and six on the 
umbilical shoulders on one volution of the younger specimen, and eleven 
on the outer and seven on the inner row of the old specimen. The bifid 
costz are also present in the younger specimen, mingled with single ones, 
as in the old stage. The keel disappears on the last quarter of the outer 
volution, both on the cast and on the shell, in the young specimen, and is 
absent also in the older one. The young shell was seen in a section of the 
specimen represented by fig. 12 of Pl. I, and although not perfect enough 
to figure, showed that when about of the same size as the young of B. 
bilobatum (Pl. I, figs. 5, 7), it had a similar keeled form. 
Locality: Cajamarca, Peru. 
Age: Upper Cretaceous. 
“See also description of R. attenuatum Hyatt. 
