: ORDOVICIAN FAUNAS. 201 
ODONTOPLEURA PARVULA (Walc.).? 
Plate XV., Figs. 21-22. 
1879. Acidaspis parvula Walcott, 31st Rep. N. Y. State Mus. Nat. 
Josey 05 (Os) 
189%. Odontopleura parvula Clarke, Pal. Minn., pt. IL, p. 744, 
fig. 61. 
Description.—Width of the cranidium along its posterior border 8 
mm., width between the eyes 5.5 mm., the outline anterior to the eyes 
forming nearly a semi-circle. Glabella proportionally large, its great- 
est width 3.25 mm., subtriangular in outline; each member of the two 
pairs of glabellar lobes entirely isolated; frontal or median lobe reach- 
ing from the extreme anterior margin of the head to the occipital 
furrow, its sides parallel and straight, with a pair of minute lateral 
extensions just back of the anterior extremity, which may, perhaps, 
be considered as a rudimentary third pair of glabellar lobes; the 
posterior pair of glabellar lobes subelliptical in outline, with their 
long axes directed obliquely to the axis of the median lobe; the an- 
terior pair about one-half the size of the posterior pair, nearly circular 
‘in outline and placed in the angles between the posterior pair and the 
median lobe. The glabellar furrows about as deeply impressed as 
the dorsal furrows. The occipital furrow broad and deep; the oc- 
cipital segment narrower than the furrow, with a small tubercle in 
its centre. Fixed cheeks nearly as prominent in their median portion 
as the lateral lobes of the glabella; palpebral lobes minute, situated 
just in front of the occipital furrow; back of the palpebral lobes the 
cheek is abruptly depressed to its long, lateral extensions. From 
the occipital furrow forward to the antero-lateral margin of the 
median lobe of the glabella the fixed cheek is marked by a marginal 
furrow, which is nearly as deeply impressed as the dorsal and glabellar 
furrows. Whole surface marked by fine, circular tubercles of variable 
size. The free cheeks, thorax and pygidium unknown. 
Remarks.—Odontopleura parvula was originally described by Wal- 
cott from the Trenton limestone of Trenton Falls, New York, but 
the description of the head is so meagre that, in the absence of illustra- 
tions, it cannot be certainly identified. The glabellar furows are 
said to be so slight that “the lateral lobes and cheeks are scarcely 
defined.” This is certainly not the case in the specimen from New 
