OF DENISON UNIVERSITY. 
17 
MOLLUSCA. 
Cephalopoda. 
Genus Ortho c eras. 
Orthoceras cribrosuin, Geinitz. (?) 
(Plate V, Fig. 2.) 
There is but one species of Orthoceras at all abundant at Flint 
Ridge, and this is invariably more or less crushed. A smaller species 
like O. rushensis, has been doubtfully identified. An average exam- 
ple of our species is from three to four inches in total length, with a 
rather gradual expansion. About a fourth or fifth part of the shell be- 
low is without visible septa and is more rapidly expanded than the re- 
mainder, which is apparently cylindrical, having moderately concave 
septa, separated by intervals of about four and one-half into the width 
of the shell. The siphuncle is apparently nearly central (?) The shell 
is very thin and the epidermis apparently unornamented or granular. 
The removal of the epidermis reveals a nodose line near one side, the 
nature of which has not as yet been determined (Cf.- O. duseri of 
Lower Silurian.) 
It is by no means certain that the identification is correct. Geinitz 
laid stress upon the pitted nature of the shell, though his figure shows 
the epidermis to have been exfoliated. 
JV’atilus sp. 
(Plate II, Fig. 17.) 
Fragments of what appears to be a Nautilus allied to N. forbesi- 
rnus, McChesney, are not rare, but none of them indicate the shell to 
have been septate. Awaiting additional material these are inferred to 
be identical with N. decoratus of Cox, identified with the above. 
GASTEROPODA. 
Genus Bellerophon. 
Bellerophon percarinatus ^ Conrad. 
(Plate II, Fig. 14.) 
Shell subglobose ; laterally expanded at the front ; umbilici closed; 
outer lip thin at fhe front, thickened by callus at the sides ; inner lip 
