244 PSEUDOCERATITES OF THE CRETACEOUS. 
smooth continuous ridges on either side that can be compared with those of 
Engonoceratide. The differences between the shell figured by Schliiter 
and the bidorsatum of Roemer are so well shown in the drawing given by 
the latter that there can be but little doubt they are different species. The 
sutures are not distinct generically from those of Placenticeras, and would 
place the species in that genus if the characters of the shell were not so 
different. 
Locality: Westphalia. 
Age: Lower Senonian. 
Incertz sedis. 
STYRACOCERAS ® n. gen. Hyatt. 
Ammonites balduri of Keyserling, the type and only known species of 
this genus, can not be associated with any species known to have same 
number of principal lateral saddles, because the external characters differ 
from those of any species known to me. ‘The resemblances in the sutures 
are certainly closer to Platylenticeras heteropleurum than to any other species, 
if Keyserling’s drawings and Neumayr’s observations are correct. The 
suture has two broad principal lateral saddles, the first and second, or else 
these may be reckoned, as in others of this group, as one saddle divided 
into two branches. Until the young are known, this can not be definitely 
decided. (See Platylenticeras.) 
STYRACOCERAS BALDURI (Keyserling). 
Ammonites balduri Keyserling, 1846, Petschora-Land, pl. 19, fig. 2. 
The young, as figured by Keyserling, has a channel on the venter in 
the neanic stage after passing through a substage with an acute venter. 
This figure may have been taken from a partly crushed fossil. So far as 
known, the replacement of an acute condition of the venter by a furrow is 
exceptional and requires more proof than a single drawing. Neumayr 
obtained the originals of Keyserling’s description and studied them, but his 
attention was not apparently attracted to this fact, and he did not break 
down any of the fossils to investigate the young. He redescribed, but, 
unluckily, did not have them redrawn, and did not state whether the 
«Srvpaé, spike on the inner end of a spear. 
