﻿454 



Figs. 6-9, PL v, show the side and front views of two speci- 

 mens, the smaller in the metanepionic and part of the paranepionic 

 substages and the other older. These are magnified to show 

 the ananepionic substages, and Figs. 6, 8, and 10 show the cicatrices 

 on the apices of both of these. The longitudinal striae shown on 

 these are necessarily exaggerated, these markings being perceptible 

 with difficulty under a magnifier. It is interesting to compare 

 these with the young of the existing Nautilus on PI. i, and it is also 

 obvious that if found without their older stages in any locality they 

 would certainly be described as cyrtoceran forms. 



Barrandeoceras (?) Elrodi. 



Gyroceras Elrodi, White {Eleventh Ann. Rep. Geol. India?ia, 

 p. 356, PI. xxxvii, Fig. 1). 



Loc, Hartsville, Ind. 



This species has an oval outline in the full-grown and senile stage 

 figured by White, with siphuncle slightly above centre by descrip- 

 tion, but slightly below centre in the figure. The living chamber is 

 not quite one-half of a volution in length, but it is very large, and 

 this, together with one-half of the last volution, are free. The 

 younger whorls are closely coiled, but not more than two and a 

 half, if so many, are in contact ; the remainder of the third and 

 first quarter of the fourth are free and the last part excentric. Dr. 

 White describes them as rounded outline in section, giving the 

 impression that there was no impressed zone. 



The rate of growth in the ventro-dorsal diameters is rapid, and 

 consequently the living chamber on the last of the third and first 

 of the fourth volution is very large, especially in the ventro-dorsal 

 diameters. 



The form and sutures are similar to those of Barrandeoceras 

 Sternberg!, and the species, if it is a member of this genus, is inter- 

 esting on account of its appearance in the Niagara group, the close 

 coiling of the young, and the length of the free whorl. 



Pycnoceras* 11. g. 



This genus has shells similar to those of Aphetoceras in the 

 nepionic stage, with siphuncle subventran, similar form in section 

 and similar sutures, with ventral and dorsal saddles and shallow 

 lateral lobes. This may be seen by comparing figures of Apheto- 



* Ilu/^dg, close. 



