258 ROYAL SOCIETY OF CANADA 
size” in the Plate. “The two principal cusps are well separated, 
unequal in size, and widely divergent; each being long and slender, 
somewhat tumid in the basal portion, and attenuated distally. The 
median cusp or denticle is subulate, long and slender. The gano- 
dentine is quite smooth.” 
The type specimen is in the British Museum, Nat. Hist. 
Original description of Doliodus problematicus. “Only a single 
specimen of this curious tooth was at Mr. Smith Woodward’s disposal, 
and that too only exhibiting the crown and denticles, being destitute 
of the root. The cusps certainly resemble those of Diplodus in form 
and arrangement, but the peculiar form of the base, which is well shown 
in many of the specimens now before me, is very different, and neces- 
sitates the institution of a new genus, which, on account of the decep- 
tive appearance of the first described example, I propose to name 
Doliodus.* 
“Instead of the thick, solid base of Diplodus we have here a broad 
thin plate, convex anteriorly and above, concave posteriorly and below, 
to the upper margin of which the crown is attached. The type speci- 
men has only one intermediate cusp, but their number may vary from 
one to three or even four.” 
(6) SPINE or (?) ACANTHODIAN. 
Homacanthus. Sp. Undt. Whiteaves. 1881. Canad. Nat. & Quart. Journ. Sc., 
vol. 10, no. 2. p. 99. 
Homacanthus gracilis, Whiteaves. 1889. Trans. Royal Soc. Canada for 1888, 
vol. vi. sect. iv. p. 96. pl. x, fig. 4. Not Homacanthus 
gracilis, Eichwald, 1869; which, according to A. S. 
Woodward, is H. arcuatus, Agassiz. 
“The spine named Homacanthus gracilis, J. F. Whiteaves (Trans. 
Roy. Soe. Canada, vol. vi, sect. iv, 1888, p. 96, pl. x, fig. 4) is also 
doubtfully determined and may belong to an Acanthodian fish resem- 
bling Climatius. The type specimen was obtained from the Lower 
Devonian of Campbellton, New Brunswick, and is preserved in the 
Geological Survey Museum, Ottawa.”—A. 8. Woodward, Cat. Foss. 
Wishes Brit. Mus. Pt. IE py 106. 
(7)  GYRACANTHUS INCURVUS, Traquair. 
4iyracanthus incurvus, Traquair. 1890. Geol. Mag., dec. 3, vol. vii, p. 21. 
The type of this species is a fin spine from Campbellton in the 
Edinburgh Museum, which is thus described by Traquair :— 
“A veritable Selachian has, however, turned up in the shape of 
a mew species of Gyracanthus, to which I apply the name G. incurvus. 

“Gr, Addioc, a deceiver.’ 
