254 NEW YORK STATE MUSEUM 
The type of the original description [pl. 36, fig. 4] is a small broadly 
triangular carapace so unusually broad that its length to width is as 2: 3. 
The lateral margins in their general direction converge to the protruding 
front of the carapace and possess a gently sigmoidal curvature, the pos- 
terior two thirds resembling projecting cheeks while the anterior third is 
concave. The postlateral angles are acute. The carapace is highest 
between the eyes, the ocellar mound being on the apex. The posterior. 
portion of the head is strongly depressed in all specimens, rising abruptly 
to the upturned lateral borders, and gradually from the base forward. A 
thickened filiform border bounds the lateral margins and a narrow, flat, 
depressed border the posterior margin. The projecting frontal margin is 
flat or slightly elevated. 
A very striking feature of the carapace is the pearllike projecting 
eyes placed very far forward and intramarginal, lying in the pit of the 
concave curve of the lateral margin. The visual surface is distinctly seen 
in several specimens [pl. 36, figs. 3, 4, 8]. It is crescent shaped and nar- 
row. The occllar mound which is situated on a line connecting the pos- 
terior extremities of the compound eyes is, like the latter, characterized 
by extreme prominence, and besides by its remarkably large relative size. 
Only one specimen has been found that can give a clue to the original 
form of the abdomen. Corresponding to the diverging lateral margins 
ot the head and its broad basis, this is also broad and widens much toward 
the posterior portion of the preabdomen, after which it probably contracted 
rapidly to the telson. 
The boundaries of the tergites are but very faintly seen and it is pos- 
sible that the specimen has suffered contraction by pressure. 
The postabdomen and telson have not been seen in place but a curved 
telson with attached last postabdominal joint [pl. 36, fig. 7] has been 
referred here provisionally, partly because it could not be placed with any 
other species and partly because the head and abdomen of E. ? cice- 
rops suggest its reference to Eusarcus and this telson points also to the 
same genus. Indeed, we consider the presence of this telson good evidence 
