METAZOA ARACHNOZOA. 373 



Peculiar modifications in the shape of the body are seen 

 in Mahadeva vernicosa Hentz (No. 922, 9 , $ ; PI. 923, 

 fig. i, 9 ; fig. 2, <). The abdomen is triangular and 

 nearly as wide in front as the body is long. The male 

 (No. 922, specimen on the right; PI. 923, fig. 2) has 

 extremely long fore legs, while the second pair are pro- 

 vided with remarkable clasping spines. 



Acrosoma (No. 924, A. gracile Walck., dorsal and side 

 views; also PI. 925, figs. 1-4) has a very different form 

 from the others already described. The cephalothorax of 

 the female (No. 924 ; PI. 925, fig. i, upper side) is small, 

 glossy, and dark colored, while the abdomen is broad at 

 the posterior end and provided with spikes on each side 

 (fig. i ; fig.' 2, lower side, x 4). Jt is flattened above 

 and is light colored (fig. i), while the ventral side is 

 darker colored and the spinnerets extend forward in a 

 conical peak to the middle of the abdomen (fig. i ; fig. 3, 

 side view of the same, x 4), giving a most peculiar ap- 

 pearance to the animal. The male (fig. 4, x 4) is very 

 much smaller than the female (fig. 2, x 4) and is distin- 

 guished by the enlarged palpal organs. 



Among the more differentiated spiders are the runners 

 like the Lycosidae and the leapers or Attidae. They 

 have a well developed cephalothorax and keen organs of 

 sense. According to the observations of the Peckhams, 1 

 the sense of sight is especially strong in these families. 



The runners, like Lycosa (No. 926) have long hind 

 legs, enabling their possessors to run swiftly while catch- 

 ing their prey. The leapers, like Phidippus galathea 

 Walck., (= Attus audax Hentz) (No. 927), have short 

 legs, the first pair being the stoutest. The Lycosidae 

 have three pairs of spinnerets, like the orb-weavers. 

 Though they do not spin webs for catching prey, they 

 construct homes for themselves in the earth, line them 

 with silk, and over them erect a chimney. 



1 The Sense of Sight in Spiders, Trans. Wisconsin Acad. Sci., 

 Arts and Letters, X, 1894. 



