196 Mr. J. Blackwall on some undescribed Araneidae. 



The male differs from the female in several remarkable par- 

 ticulars ; it is smaller, and presents, exclusively, some of those 

 peculiarities of structure on which the generic character is 

 established. The lateral margins of the cephalothorax are 

 strongly dentated, and a series of short sharp spines, slightly 

 curved forwards, occupies the medial line of its anterior con- 

 vexity; each mandible also has a longitudinal row of spines, 

 curved downwards, on its exterior side. (Small spines occur 

 sometimes on the mandibles of old females.) The second joint 

 of the palpi is greatly elongated, much curved, and is armed 

 with strong spines beneath ; the third and fourth joints are 

 dilated at their anterior extremities, the former having a large 

 conical apophysis on the lower side, and the latter two ter- 

 minal apophyses, one short and broad projecting in front, the 

 other more elongated and acute situated underneath ; the fifth 

 joint is oblong-oval, convex externally, concave within, com- 

 prising the sexual organs, which are highly developed, and 

 of a very dark red-brown colour. The relative length of 

 the legs likewise is different in this sex ; the first pair is the 

 longest, measuring ith of an inch, and the fourth, second, 

 and third pairs decrease successively in longitudinal extent. 

 These organs and the palpi are much redder than those of 

 the female. 



Independently of colour, the spider described above may 

 be distinguished by its external structure from the Erigone 

 vagans of M. Savigny. [Description de FEgypte, seconde edi- 

 tion, tome xxii. p. 319 — 321 ; Atlas de Zool. ; Arachn. pi. i. 

 fig. 9.) The male of the latter species has three rows of spines 

 on the anterior convexity of the cephalothorax ; a single row 

 on the under part of each thigh of the first pair of legs, and 

 the second pair of legs is longer than the fourth ; whereas the 

 new spider has only one row of spines in the former situation, 

 and none in the latter, a few very minute ones merely occur- 

 ring on the inner side of the thighs of the fore legs, near their 

 base, and the fourth pair of legs is longer than the second ; 

 moreover, each palpus of the female of Erigone vagans has a 

 pectinated claw at its extremity, but the palpi of Erigone atra 

 are destitute of claws. 



This diminutive spider is very plentiful and decidedly diur- 

 nal. Endowed with an instinctive impulse to ascend into the 

 atmosphere, it frequently takes aerial excursions, and is active 

 even in winter, when the weather is mild. It pairs in June, 

 and deposits its eggs, which are large in proportion to the size 

 of the animal, six or seven in number, spherical, not agglu- 

 tinated together, and of a pale yellowish-white colour, in a 

 cocoon of white silk, of a slight texture, and subglobose form, 



