224 PSEUDOCERATITES OF THE CRETACEOUS. 
saddles; the others were covered and could not be seen. The only exposed 
suture immediately preceding the constriction has entire outlines. The 
ventral lobes are moderately deep and straight-sided, with large, undivided 
siphonal saddle. The first lateral saddle is rounded and broad, but entirely 
upon the venter, as is also the first lateral lobe. The latter is also rounded 
and wide at base and not so deep as the ventral lobe. The second lateral is 
magnosellarian in outline and reaches to the small lobe formed on the line 
of involution. It is interesting to note that in this highly degenerate form 
of the Cretaceous the sutures exactly resemble at this age the adults of the 
Primordialidee, which have undivided siphonal saddles, and the volution 
on section has the semilunar anarcestian form of the nepionic stage in 
Ammonitinee.“ 
Near the end of the first volution the first lateral saddles and also the 
magnosellarian saddles have begun to show minute dividing lobes. The 
form in section has at the same time changed to helmet shape through the 
elevation of the venter. The zone of involution at this age begins to 
increase and in the next volution extends over nearly the entire side of 
the first whorl. In consequence of the helmet shape and flatness of the 
sides the involution, which is about two-thirds, appears to be greater 
than at any subsequent stage, whereas it is proportionately less. The 
ananeanic substage begins on the second volution. The sides become 
flatter, more convergent, and the venter is narrowed and flattened on the 
cast and slightly concave on the shell. In the metaneanie this change is 
completed by the rapid increase of the dorso-ventral as compared with the 
transverse diameter. The venter still remains quite broad and does not 
attain the narrow aspect of the adult until in the latter part of the neanic 
stage on the fourth volution. The umbilical zone begins to develop in the 
ananeanic substage and steadily increases in breadth and steepness there- 
after. The auxiliary lobes and saddles begin to appear in the paranepionic, 
and as the volution increases in the ventro-dorsal diameter more of them 
are introduced by the further division of the magnosellarian saddle, or 
rather what remains of this, in the umbilical zone. The process of division. 
continues throughout the neanic stage, the additions being made internally 
on the umbilical shoulders and zone. They arise as simple indentations 
and grow deeper with age, the digitations being introduced gradually by 
-@The margin of the manuscript bears a large ‘‘?’’ opposite this sentence.—T. W. 8. 
