PLACENTICERATID &®. 241 
schliiteri, and all the tubercles and costz occur only in old age, according 
to the figures, whereas in the latter they are present in adults as well as in 
the gerontic stage. 
Age: Lower Senonian. 
PLACENTICERAS CRASSATUM n. sp. Hyatt. 
Ammonites syrtalis var. orbignyanus Schliiter (pars), 1872, Paleontogr., Vol. XXI, 
pl. 14, figs. 4-7, fig. 3% (no others). 
This species differs from schliiteri, being more compressed. The 
recession outwardly on the inner row of tubercles does not take place. 
The inner row of tubercles disappears in what is probably the anagerontic 
substage, and in this also fold-like costee are developed. The venter 
remains flattened, the sides flat, and the ventral tubercles are still well 
developed in this substage. 
Age: Lower Senonian. 
PLACENTICERAS TAMULICUM (Blanford). 
Ammonites tamulicus Blantord, 1863, Mem. Geol Sury. India, Vol. 1V, p. 118. 
Ammonites quadalupe Stoliczka, 1866, Pal. Indica, Vol. I, pl. 47, and pl. 48, fig. 1. 
Placenticeras tamulicum Kossmat, 1895, Beitr. Pal. und Geol. Oesterreich-Ungarns 
und des Orients, Vol. IX, pl. 22, figs. 1 a-c. 
The neanic stage of this Indian species is figured by Kossmat, and 
this, together with the figures by Stoliezka, shows that this shell had a more 
compressed form, flatter sides, narrower ventral zone, and different sutures 
in the adult and less prominent and less distinct costations than the 
gibbous-sided form, also included in this species by Stoliezka in Paleonto- 
logia Indica and figured, pl. 47, fig. 2, sutures being also given, fig. 2a. 
There are considerable variations in the shapes of the saddles, between the 
last figure and those of tamulicum (guadalupe) on pl. 48, fig 1, which can 
hardly be accounted for by differences of age in the specimens. It is difti- 
cult of course to say to which of the two forms the large specimen on 
pl. 47, fig. 1, may belong, and any attempt to separate them under different 
names would not be advisable. This last figure, 183 mm. in diameter, is 
in the gerontic stage and shows a second external row of nodes of large 
size and the inner row increasing greatly in size to blunt nodes on the last 
part of this volution. None of these authors mentions any rounding-off of 
MON XLIV—03—— 16 
