374 ON THE TEDIPALPI OF NORTH AMERICA. 



Posteriorly, in the median line, there exists a depression, mostly well-marked , from 

 which radiate obsolete grooves. Anteriorly the carapace is rapidly narrowed, but is 

 is possessed of a vertical aspect elsewhere wanting, having a sharp edge between 

 it and the upper surface. The median pair of eyes are situated on a tubercle. 

 They are sensibly larger than the lateral. At the hinder end of the edge formed 

 by the folding clown of the dorsal shield, spoken of above, are the posterior or 

 lateral eyes, arranged in the form of a triangle, three on each side. The upper 

 surface of the abdomen is generally roughened, like the cephalothorax. The lower 

 surface smooth. The specific characters are principally founded on the aspect and 

 armature of the maxillary palpi. There has as yet only a single species been found 

 in the United States. 



T. Giganteus. — T. saturate rubro-castanco ; cephalothorace enormiter subrude punctata ; palpis crassis, 

 maximis, rude punctatis, in femina longis, in mare longissimis ; articulo secundo supra quin- 

 que spinoso, infra bispinoso ; tertio et supra et infra unispinoso ; quarto supra spina maxima 

 longissimaque, spinas marginibus antico et postico denticulato ; quinto extra spina maxima et 

 crassissinia, spinas marginibus et antico et postico denticulato ; digito crassissimo, infra et supra 

 valde denticulato. 



Thelyphonus giganteus, Lucas, Magazin de Zoologie (Guerin) 1835, cl. viii. pi. 8. Gervais, Apteres, iii. 

 p. 12. Koch Arachmden. Bd. x. p. 21, Fab. 331, fig. 767, et Fab. 332, fig. 768. 



Thelyp. excubitor, Girard, Marcy's Report of Explorations of Red River, p. 265, fig. xvii. 1-4. 



The general color of this species is very deep reddish-chestnut. The ventral surface 

 is much lighter than the dorsal. The sides of the abdomen of the female when dis- 

 tended with eggs, are of a fawn tint, spotted with black. The cephalothorax is very 

 rough, with its surface irregularly rudely punctate, or perhaps more properly exca- 

 vated. It has an interrupted mesial groove. The maxillary palpi are very massive 

 and long. In the female they are much longer than in the male. The former sex is 

 the Thelyp. excubitor of Girard. This we have proven by the dissection of a num- 

 ber of individuals ; a figure of each sex is given by Koch. The first or immovable 

 joint of the palpi has its anterior spine large and curved. The second has its 

 superior surface expanded anteriorly into a broad, spine-like process. The curved 

 margin of this is armed with five short stout spines. The third joint, superiorly. 

 is provided with a robust spine, inferiorly with one generally fully a line in length. 

 The legs are stout, tuberculate, and sparingly pilose. The abdomen is distantly, 

 coarsely, and thickly minutely punctate. The larger punctations on the superior 

 surface are often quite peculiar, appearing somewhat like the teeth of a rasp, as if 

 they had been punched out. 



Hub. — South Western United States, Mexico. 



