380 NEW YORK STATE MUSEUM » 
the fact that the known fragments of Pterygotus cobbi, from the 
same locality and formation, also represent a colossal animal, it 1s pos- 
sible that the rami of P. cobbi and the telson of P. grandis will 
prove to belong to the same animal. 
Pterygotus monroensis Sarle 
Plate 70, figures 3-5 
Pterygotus monroensis Sarle. N. Y. State Palaeontologist Rep’t. 1902. 
p. 1102, pl. 24, fig. 7, 9 
?Pterygotus sp. Sarle. bid. p. 1104, pl. 24, fig. 6, 8 
Sarle describes this species as follows: 
This species is founded on a single specimen, a cephalothoracic shield. 
The outline of this shield is semieliptic with the posterior edge noticeably 
incurved. The surface is moderately convex, and along the sides and 
front is a threadlke border.. The length of the shield, without the genal 
angles, is 30 mm, with them 37 mm; the breadth at the base 38 mm. 
The compound eyes are prominent and project beyond the outline of 
the shield. They are subelliptic, with a distinct angulation on the inner 
side of each, produced by an indentation of the inner anterior part. They 
are 14.5 mm long and 6 mm wide. The facets can be made out with 
a good magnifying glass. The eyes are located a distance equal to their 
own length from the front of the shield and 27 mm from each other. 
A line connecting their bases cuts the axial line a little back of the center 
of the shield. The ocelli are on a small tumescence just back of this. The 
ornamentation is almost obliterated, but can be made out at one point, 
where it consists of minute, short, flat, lobelike scales. 
Its differences from P. macrophthalmus are also indicated 
by the author as follows: 
The cephalothorax of this new species differs from that of P. mac- 
rophthalmus in that its length is nearly equal to its breadth; 
the compound eyes are over one third the length of the shield, elongated, 
angulated on the inner side, situated farther back, and separated by 
nearly twice their length. In P. macrophthalmus the length 
of the shield is three fourths the breadth; the eyes are about one third 
the length of the shield, anterior, globular and separated by a distance 
about equal to their length. 
The type specimen, which is in the State Museum, possesses some 
characters quite suggestive of a more proper reference to Hughmilleria. 
Sarle remarks that the form of the eyes suggests those of ‘““P. bilobus 
