104 



Report of the State Geologist. 



ventro-lateral saddle, has not yet appeared, but at three and one-half volutions 

 the ventral saddle has become very broad and its division probably imme- 

 diately follows. At this stage of growth there is, also, but a single sub- 

 lateral saddle, a lateral and an umbilical lobe ; and of all lobes and saddles only 



the ventro-lateral lobe is acute. At 

 Ad u \t K the opening of the third volution the 



form of the suture is gephyroceran, all 

 auxiliary lobes and saddles being still 

 undeveloped and duringthe course of 

 the second win >rl the suture is distinctly 

 anarcestian. Further than this there 

 is little to be now said with reference 

 to the variations in growth. The 

 stages referred to have been made out 

 largely from immature individuals and 

 it will be observed that, as we have 

 already had occasion to remark, the 

 ephebic, condition of the Pkobeloceras 

 suture does not clearly appear in any 

 of these stages. Better material may 

 show that it is closely approached in 

 the course of the first half of the third 

 whorl before the introduction of the 

 sublateral saddle and while the suture 

 is gephyroceran. Even here its lobes 

 and saddles are rounded, not acute 

 as in the ultimate condition of Pko- 

 belocekas and Beloceras. It is, however, important to note that Pkobelo- 

 cekas presents an immature phase of the suture which would agree through, 

 out with such a condition. 



Distribution. Beloceras iynx is found associated with Probel. Luiheri 

 in the Portage shales and appears to be considerably the less abundant of the 

 two. It has thus far been observed only in localities of the lower part of the 

 formation at Naples. 



2. J vol. 



Figure 77. Beloceras iynx 

 septal sutures. 



The development of the 



