Mr. MacLeay on some new forms of Arachnida. 11 



the former is the shortest joint, and the last is by far the 

 thickest, being truncated and concave at the apex. 



Labial palpi pediform and 7 -jointed, only the basal joint is 

 evanescent. 



Mentum oval, elongate. 



Body with a subcrustaceous tegument. Head distinct from 

 thorax though soldered to it ; quadrate and convex on 

 the upper side, where the eyes are placed. Thorax ovate, 

 narrower and longer than the head, and convex also on 

 the upper side. Abdomen subarticulate, arched, pedun- 

 culated at the base, swelling in the middle, with a con- 

 vex back and dilated margined sides, and then termina- 

 ting in a spindle ; the peduncle before mentioned being 

 slender, cylindrical, and longer than the head. Feet are 

 like the labial palpi, but the two first pair are somewhat 

 shorter. Ungues not very conspicuous. 



Sp. 4. Myrmaraciine melanocephala. — Myrmarachne capite nigro; an- 

 tennarum articulo primo rufo basi flavo ; palpis maxillaribus brunneo- 

 nigris; thorace abdominisque pedunculo rufis; abdomine nigro ; palpis 

 labialibus pedibusque piceis. 



Long. 4£ lin. 



This handsome spider is a native of Bengal, and I present a 

 figure of it, made by my friend Mr. C. Curtis, in order to show 

 the relation which it bears to the American subgenus, called 

 Myrmecium by Latreille. Myrmarachne is even still more like 

 than Myrmecium to an ant or Mutilla, Its hard corneous en- 

 velope, its distinct head, the long peduncle of its abdomen, 

 and its insected body, all tend to aid the deception in the 

 most striking manner. It evidently comes between Alius 

 formicoides, Walck., and Myrmecium rufum, Lat. It has the 

 eyes of the former spider, except that the two smallest and 

 middle ones are not placed at the margin of the head. With 

 the latter spider it agrees in the head being even still more 

 perfectly distinct from the thorax, as well as in the abdomen 

 being subarticulate. Myrmecium, however, in its eyes, ap- 

 proaches, as Walckenaer observes, to Dolomedes, while the 

 antennae are short and of an ordinary form. 



In Myrmarachne melanocephala the antennae are long, stout, 

 and the first joint has a tubercle on the upper side of its apex, 

 and its whole plane upper side is transversely striated. No- 



