218 NEW YORK STATE MUSEUM 
for this reason be unwarranted to unite it with the latter subgenus, espe- 
cially since both lived under unlike abnormal marine conditions, that 
is, Tylopterus in very saline water, Anthraconectes in brackish or fresh 
water. 
Tylopterus boylei (Whiteaves) 
EKurypterus boylei Whiteaves. Paleozoic Fossils, v. 3, pt 1. 1884. p. 42, 
pl. 7, fig. 3 
The species was very carefully described by Whiteaves as follows: 
Carapace moderately convex, broader than long, greatest breadth a 
little above the middle; semiovate, broadly rounded in front and squarely 
truncated behind; sides somewhat convex at their margin above, but 
straighter below; front and sides bordered by an elevated, narrow ridge, 
which is highest and most strongly marked on the posterior half of the 
sides. Eyes reniform, prominent, about 4 mm in the greatest diameter; 
9 mm apart (as measured from the center of their inner margins) and 
placed at a distance of 6 mm from the anterior, and of 7 mm from the 
lateral margin. Ocelli not clearly indicated, but probably placed on or 
near a small rounded prominence or elevation, which is situated exactly 
in the middle of the space between the two eyes. Surface of the carapace 
apparently finely granulose, and ornamented with minute rounded tuber- 
cles, some of which are isolated and others confluent in sets of two or three. 
Thoracic and caudal portions together consisting of 12 segments, 
exclusive of the telson or caudal spine; the first, second, third and fourth 
thoracic segment each bearing on the median line a single, large and prom1- 
nent, transversely elongated tubercle, which is arcuate or reniform at its 
base and somewhat bilobate at its surnmit. The lateral diameter of each 
of these tubercles greatly exceeds the longitudinal, and measuring at their 
base, the proportions of each tubercle may be thus approximately estt1- 
mated; that on the first thoracic segment, lat. diam. 4 mm, long diam. 
not quite 1 mm; that on the third, lat. diam. nearly 5 mm, long diam. 
rather more than 1 mm; that on the third, lat. diam. 5 mm, long. diam., 
2 mm; and that on the fourth, lat. diam. 54 mm, long diam., 3 mm. 
Telson produced into a gradually narrowing, slightly curved, and 
rather obtusely pointed linear spine, which seems to be triangular in 
transverse section. 
Antennae, endognaths and ectognaths unknown, as js also the nature 
of the surface markings of the test of the thoracic and caudal segments. 
Entire length, including the telson, about 75 mm (or 3 in.); length 
of carapace, 20 mm, greatest breadth of the same, 27 mm; length of telson, 
I5 mm. 
