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 ro show the cicatrices 
on the apices of both of these. The longitudinal strizs 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 Pl. 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. 
GyYROCERAS ELropi, White (Z/eventh Ann. Rep. Geol. Indiana, 
pra5O; Pl. xxxvil, Pig. 2): 
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 
Sternbergi, 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,* n. 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- 
* Tluxvos, close. 
