S. polymorpha
S. olivaceo-brunnea; capite dilute castaneo; segmento cephalico subovato, postice subtruncato, fere impunctato; antennis 30 articulatis; dente mandibulari tuberculo basali magno; dentibus labialibus 8, maxinris, duobus intimis utrinque coadunatis, externis sejunctis; scutis interdum margine posteriore nigro-viride, marginibus lateralibus plerumque liberis; pedibus postremis robustis, supra subcomplanatis; articulo basali subdepresso, intus 3—7 spinis, subtus 10—18 spinis in serie quadruplici (interdum inordinatim) dispositis, processu angulari aut bifido aut trifido aut quadrifido; appendicibus analibus lateralibus singula 4—8 spinis apicalibus et altera marginali.
Olive-brown; head light chestnut; cephalic segment subovate, posteriorly subtruncate, almost impunctate; antennæ 30 articulate; mandibular tooth with a large basal tubercle; labial teeth 8, very large, the inmost two on each side coadnate, the external distant; scuta sometimes with the posterior margin blackish-green, the lateral margin generally free; last pair of feet robust, above subcomplanate; basal joint, and median also, subdepressed, within with 3—7 spines, below with 10—18 spines arranged in a fourfold series (sometimes irregular), angular process either bifid, trifid, or quadrifid; lateral anal appendages, each with 4—8 apical spines and a marginal one.
S. polymorpha, Wood, Proc. Acad. Nat. Sci., 1861, p. 11. Journ. A. N. S., new series, 1863, p. 20.
The prebasilar fold is apparent but connate with the rather large basilar segment. The first segment of the body is very small; the scuto-episcutal suture are barely traceable, but the sterno-episternal are much more distinct. In a few individuals the labial teeth are small and coadnate. The color shades off from that given above to a testaceous chestnut. This species is closely allied to S. heros, and perhaps a differential diagnosis would not be amiss. The most important difference is in the number of joints to the antennæ. Owing to the ease with which these animals lose portions of these organs, the want of the typical number is not to be relied on in the identification of individuals. Another character which also is often not available for individual identification, but which characterizes this species, is the small size attained to. The spines of the lower surface, of basal articulations of last pair of legs, are more numerous than in S. heros, and arranged in four rows instead of three. The difference in arrangement is, perhaps, more apparent than real; the homologue of the first row of spines existing in some specimens of S. heros, but being placed a little higher up, they are thrown with those on the inner side of the limb. The angular process has fewer spines than in S. heros. Finally, although the species do exist on common ground, yet heros is a more tropical and polymorpha a more boreal animal, the regions which they occupy merely overlapping somewhat. Length 3½ inches.
