AMERICAN PALEOZOIC CEPHALOPODS 
217 
and Glossoceras the exterior of the shell is smooth. In Aphrag- 
mites the exterior of the living chamber is sharply annulated 
transversely. 
In American strata the genus Ascoceras is represented by the 
species Ascoceras indianense Newell from the Niagaran at 
Delphi, Indiana, Ascoceras southwelli Worthen from the Niaga- 
ran at Port Byron, Illinois, and Ascoceras townsendi Whiteaves 
from the Niagaran (Guelph) at Durham, Ontario. In the last 
named species the gerontic group of living chambers appears to 
have been relatively much shorter than in typical forms of 
Ascoceras. 
16. BILLINGSITES HYATT 
Genotype: Ascoceras canadense Billings. Rep. Progress for 1853-56, 
1857, Geol. Surv. Canada, p. 310; Geol. Canada, 1863, p. 318, fig. 227 
Billingsites differs from typical Ascoceras chiefly in having 
the gerontic group of living chambers dorso-ventrally depressed, 
instead of laterally compressed as in the latter genus. The con- 
tracted part of the living chamber, above the level of the upper- 
most dorsal saddle, is much shorter in Billingsites and is more 
distinctly depressed dorso-ventrally. The margin of the aper- 
ture is transverse, without crests or sinuses. The genus is 
known so far only from the Ordovician. 
The genus Billingsites includes Billingsites articostiensis (Bil- 
lings) from the Gamachian (Ellis Bay) of Gamache Bay, Anti- 
costi; Billingsites borealis (Parks) from the Richmond (Sham- 
mattawa) of Shammattawa river, Manitoba; Billingsites costu- 
latus (Whiteaves) from the Richmond of the Lake Winnipeg 
region in Canada; and Billingsites newberryi (Billings) from 
the Richmond (English Head and Vaurial) and Gamachian of 
English Head and other localities on Anticosti. The genotype is 
Billingsites canadensis (Billings) from the English Head and 
Vaurial of Anticosti. 
The specimen described by Sardeson under the name Ascoceras 
gibberosum, from the Ozarkian (Oneota) of Dresbach, Minne- 
sota, according to Dr. E. 0. Ulrich belongs to a new genus of 
Chiton, related to Priscochiton, now under investigation. 
17. BILLINGSITES (?) WILLIAMSPORTENSIS SP. NOV. 
PLATE XXXV, FIGS. 2A, B, C 
The specimen has the external form of the gerontic living 
chamber of a Billingsites. It is depressed dorsoventrally, and 
the more convex side is regarded as ventral, the less convex as 
