TRILOBITES. 719 
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Fig. 29.—Outline of head of Illenus crassicauda Wahlenberg, viewed from in front. 
Bumastus trentonensis.] 
Dr. Emmons in 1842 noticed, under the name I//a@nus trentonensis, asmall Bumastus 
from the Trenton limestone at Watertown, N. Y., giving a profile and dorsal view of 
a single entire specimen. These figures are here introduced. In the same place he 
gave a figure of a much larger and quite distinct species, from presumably the same 
horizon, referring to it by the name Bumastus trentonensis. This use of the same 
specific name for species evidently distinct, and which the author regarded as 
generically different, has been the source of the confusion of the two. Illenus 
trentonensis Emmons, has not been recognized by later writers; Bumastus trentonensis 
Emmons was referred by Hall (Joc. cit.) to Illenus, while Emmons’ Il/enus trentonensis 
was not noticed by this writer. This involution of names is the probable cause of 
both of Emmons’ terms being referred to I. trentonensis in the catalogues of Miller 
and Vogdes. ; 
The Bumastus trentonensis Emmons (I. trentonensis Hall), as represented in the 
original figure, is a large species with I//enus-like cephalon and broadly lobed thorax 
and pygidium. The longitudinal lobation is so pronounced, and the median lobe 
of the body so narrow, as to make the reference of the species to Bumastus 
incongruous. It appears from the description of this species given by Mr. Hall (Joc. 
cit.) that the original specimen was lost, and that his account, as well as his figure 
of it, was drawn from a plaster cast. One or the other of these figures must have 
been quite inaccurate, for the latter represents a fossil in which the lobation is 
altogether obsolete, except for the faint evidences of dorsal furrows upon the 
cephalon. The animal, as represented thus, would be an excellent Bumastus. Tam 
Figs. 30, 31.—Bumastus trentonensis Emmons (sp.). Copies of the orginal figures of the species. 
disposed to believe the original figure the more reliable; it is certainly the more 
natural in appearance, and was executed by Mr. Ebenezer Emmons, jr., whose 
skill as a delineator of fossils is widely and favorably known. We may safely 
leave to this species the name I//enus trentonensis; and shall therefore revive for 
