large, and distally very hairy. They are each armed with two large and two small spines. The longer and more slender of the former at its proximal portion is bent rather abruptly at right angles to itself, but is nearly straight afterwards. The more robust is nearly straight, save at its distal extremity, where it is abruptly bent at right angles to itself. It is armed with several very slender spinules, and has one edge distantly and obsoletely denticulate. Of the smaller spines, one is short and blunt; the other much longer, sharp, slender, and falciform. The last scutum is triangular, and has its apex truncate and very slightly decurvate. The preanal scale is semi-orbicular. Length, 2 to 3 inches.
Hab. Mississippi.—Museum of Smithsonian.
Subgenus LEPTODESMUS.
Corpus subcylindricum. Dorsum valde convexum. Laminæ laterales parvæ.
Body subcylindrical. Dorsum very convex. Lateral laminæ small.
P. placidus.
P. olivaceo-brunneus, scutis plerumque nigro vittatis; laminis lateralibus parvis, dilute brunneis; pedibus saturate olivaceis; sternis dilute brunneis; appendicibus (Fig. 56) masculis, valde elongatis; spina terminale magna, in spiram ducta et spinulo basali longissimo falciforme et altero laterale breve robusto instructa, margine partim acute serrato, partim integro.
Olive-brown; many of the scuta banded with black; lateral laminæ small, light-brown; sterna light-brown; male appendages strongly elongate; terminal spine large, spiral, furnished with a very long, falciform, basal spinule, and a second short, robust, lateral one; its margin partly entire, partly acutely serrulate.
P. placidus, Wood, Proc. Acad. Nat. Sci., 1864, p. 9.}}
Fig. 56
The head is dark-colored. Besides its median furrow, it is ornamented with a pair
of sometimes illy pronounced puncta on each side of the vertex. Its inferior border is
rather broadly emarginate. The antennæ are elongate, dark-brown, and
tipped with black. The anal scutum agrees with the others in color. It
is triangular, with its apex truncate, obscurely emarginate and decurvate.
The male genital appendages are strikingly elongate. The terminal spine
is nearly black. It is bent spirally on itself, but after performing a little
more than an entire turn is nearly horizontal for some length. It is flattened, with its superior surface somewhat umbonate, and ends in a thick,
blunt, spine-like process. The proximal portion of the anterior margin is
acutely serrate. From the edge projects a short thorn-like spinule, and
from the base a long, slender, falciform spine. Length, 1¼ inches.
Hab. Michigan.—Prof. Miles.
vol. xiii.—29
