21S DESCRIPTION OF THE SPECIES OF PTERYGOTUS 
11, but the surface of the cuticle is generally roughened between the 
plice. Some segments show the plica very large, fig. 2, and must 
have been at least fourteen inches broad. Other specimens in the 
Ludlow Museum show four or five rings overlapping, and some are 
subcylindrical, and with sharp edges. The caudal joint (twelfth) is 
broad-oval and shortly apiculate, less abruptly so than in P. anglicus, 
which, too, has a less regularly oval form, the greatest breadth 
being below the middle. It is marked all the way down dorsally 
by a strong carina covered with broad squame, and the edges 
are also squamate, in two or three rows. In the specimen from 
Trimpley, fig. 12, the sides are marked by oblique radiating interrupted 
lines. 
Epistoma and Labrum (not figured)—This plate is as large as 
that of P. anuglicus, Plate III. [Plate 14], and nearly like in all its 
parts to it. 
lntenne, Plate XII. [Plate 23] figs. 1,2; Plate XIV. [Plate 25] 
fig. 10.—These resemble in general form those of P. anglicus, but 
have a more slender shaft, tapering more quickly, and narrower 
and more conical teeth. The teeth are intermediate in form between 
the species above mentioned, and P. prodlematicus, the central one 
being long-lanceolate, and the secondaries narrow, conical, and with 
coarse stria. The base of the fixed claw, Plate XIV. [Plate 25] 
fig. 10, is furnished with a set of stiff spines, as in P. problematicis, 
but the whole chela is proportionably much shorter. 
Endognaths, Plate XIV. [Plate 25] figs. 5, 6, 7—Of these there 
seem to be two pairs, as in P anglicus, and of very similar shape. 
The one pair (fig. §) resembles in all respects Plate VII. [Plate 18] 
fig. 5, except that it has the teeth more bent down. The joints 
of the palpus, like those of P. gzgas, have a squamose ridge along 
each side, and the ends of the joints are bilobed. The second joint 
is three and a quarter times as long as broad. This is nearly the 
proportion in P. anglicus, where it is three times the breadth. 
The other pair of jaws (fig. 7) have their anterior margin more 
curved, and the teeth set on a more convex edge than in P. anglicus. 
The first tooth @ is set more backward, thick, and curved at its base, 
and all are more curved than in the Scotch species. 
The Post-oral Plate (Plate XII. [Plate 23] fig. 3) may belong 
either to this or to P. gigas. 
Base of Swimming Foot, Plate XIV. [Plate 25] figs. 8, 9.— 
These portions are very characteristic in all the species. In this the 
shape most nearly resembles that of P. gzgas, Plate [X. [Plate 20] 
fig. 8, and the teeth are short and blunt, as in that species, but the 
