Mr. MacLeay on some new forms o/* Arachnida. 5 



Walck., or Tessarops. Tessarops is a genus described by 

 Rafinesque in the ^ Annales des Sc. Phys. de Bruxelles/ and 

 to which some doubt is attached. Although I have no hesi- 

 tation in admitting that spiders may occur with four eyes as 

 well as with two, six, or eight ; stiU the magnified hind leg as 

 figured by Rafinesque, and other circumstances connected 

 with the pecuhar character of the author, make me agree with 

 Latreille in considering the existence of Tessarops marithna 

 as extremely apocryphal. If any such being exists, I suspect 

 it will be found to have been most incorrectly described. At 

 all events, I cannot believe it properly placed by LatreiUe 

 among the saltigrade spiders ; nor do I think it can on the 

 other hand be very nearly allied to Nops. It seems, if I may 

 be allowed to found a conjecture upon a figure so bad and a 

 description so lame as those of Rafinesque, to be more closely 

 connected with a singularly flat and minute hard-shelled six- 

 eyed spider with a sessile abdomen, which is to be found in 

 Cuba among old papers and in boxes of insects, and which 

 passes off directly to the Acaridea or order of mites. I have 

 called it Sclerachne ; for its tegument is even more hard in 

 proportion to its size than that of the genus Gastracantha of 

 Hahn, or any of the cancriform Epe'iridce which form Wal- 

 ckenaer's genus Plectanus. 



Plate I. Fig. 1. Nops Guanabacoee magnified. 



Genus SELENOPS, Dv/our. 



Antennce short, with the first joint subconical, and the second 

 joint or fang hooked and sharp. 



Eyes eight, six of which are placed in a semicircle with the 

 arch convex forward, the two lateral ones being the 

 largest and rather further removed from the intermediate 

 four than these are from each other. The remaining two 

 eyes, which are the least of all, are anterior, placed one 

 on each angle of the head and nearly on the same line 

 with the two middle ocelli of the semicircle. 



Maxillce straight. 



Maanllary palpi having the first joint very minute. 



Labial palpi pediform and seven-jointed. 



Mentum rounded at apex. 



