AND DEVONIAN CONODONTS. 357 
with a groove like that of the main tooth at the back. They are 
frequently unequal in length and in the number of denticulations in 
the same specimen. ‘These vary from 4 to 11, and are either short 
and blunt, or long, pointed, and slightly curved, in some cases of 
equal length on the same base, but frequently the central denticula- 
tions are the longest. 
The teeth are smooth, black, and, where not much weathered, 
of a brilliant polish. The length of the central tooth varies from 
3 line to 12 line, the greater number are about 1} ]ine. The lateral 
extensions vary between one third and two thirds the length of 
the main tooth. Though there is a great difference in form and 
size in these teeth, the extremes are connected by so many interme- 
diate forms as plainly to indicate that all belong to a single species, 
and no other form but this appears to be present in these rocks. 
This species is closely allied to P. Volborthii, Pander (Monogr. 
p- 30, tab. i. fig. 1), from which it may readily be distinguished by 
the basal termination and the deep longitudinal groove of the main 
tooth, and the proportionately less development of the lateral exten- 
sions. J am unable to make any comparison of the relative dimen- 
sions of this and Pander’s species, as unfortunately no reference is 
made by him either to the actual size of the specimen or to the 
scale to which the figure is drawn. 
The species is abundant and well preserved, and occurs in beds of 
dark limestone, principally composed of the tests of Leperditia. 
Loc. Grenville on the Ottawa River, province of Quebec. 
2. Conodonts from the Cincinnati Group. 
Genus Drepanopus, Pander, 1856. 
Drepanopvs arcuatus, Pander. (PI. XV. figs. 7, 8.) 
Drepanodus arcuatus, Pander, Monographie der fossilen Fische, 
1856, p. 20, tab. 1. figs. 2, 4, 5. 
Tooth simple, resembling a more or less curved spine, nearly cir- 
cular in section, the basal portion expanded and with a slight 
contraction between it and the shaft of the tooth. The teeth are 
all translucent and of a reddish horn-colour ; they vary in length 
from 2 line to 1} line, and in width at the base from j line to # line. 
Loc. Garrison Common, near Toronto, Ontario. Abundant. 
Genus Distacopus*. 
Machairodus, Pander, 1856. 
Disracopus incurvus, Pander. (Pl. XY. fig. 9.) 
Machairodus inewvus, Pander, Monographie der fossilen Fische, 
p. 23, tab. i. fig. 22. 
Base of tooth expanded, the shaft slightly curved, the point com- 
* I propose to substitute this name for Pander’s Machairodus, the latter 
haying been long preoccupied by Kaup. 
