158 mi: MVK1AP0DA OF NORTH AMERICA. 



S. POLYMORPH A. 



S. olivaeeo-brunnea ; capite dilute castaneo ; segmento cephalico subovato, postice subtruncato, fere impunc- 

 fcato; antennis 30 articulatis ; dente mandibulari tuberculo basali magno; dentibus labialibus 8, maximis, duobus 

 intimia utrinque coadunatis, externis sejunctis; scutis interdum margine posteriore nigro-viride, marginibus 

 lateralibus pleruinque liberis; pcdibus postremis robustis, supra subcomplanatis; articulo basali subdepresso, 

 intus 3 — 7 spinis, subtus 10 — 18 spinis in scric quadruplici (interdum inordinatim) dispositis, processu angulari 

 aut bifido aut trifido aut quadrifido; appendicibus analibus lateralibus singula 4 — 8 spinis apicalibus et altera 

 niarginali. 



Olive-brown; bead light chestnut; cephalic segment subovate, posteriorly subtruncate, almost impunctate; 

 antenna' 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 mar- 

 ginal one. 



S. polymorpha, Wood, Proc. Acad. Nat. Sci., 1861, p. 11. Journ. A. N. S., new series, 1863, p. 20. 



The pvebasilar 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 trace- 

 able, 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 

 antennae. 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 ,V. 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. Inn,*, 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 thej occupj merely overlapping 

 somewhat. Length V^ inches. 



