126 



AMERICAN SPIDERS AND THEIR SPINNINGWORK. 



to as " sternal cones," or simply " cones ' 

 iriaxillse (mx) are also shown in Fig. 92. 



VII. 



(s.co). The labium (lab) and 



The parts of the abdomen referred to in description are as follows : 

 The dorsum (Fig. 93, do) is the rounded top of the back, of which the 

 anterior part is called the " base " (ba), and the posterior the 

 "apex" (ap). The "folium" (fol) is a leaf like figure which usually 

 occupies one-third or more of the middle jiart, extending longitudinall}' 

 from base to apex. The median line (mn) of the dorsum often has a 

 deeper shade of color than the edges of the folium. The blackish " pits," 

 or round dark spots (pt), sjanmetrically arranged in pairs on each side of 

 the median line of the folium, indicate points of attachment for internal 



muscles. The venter 

 (vn, Fig. 94) is the part 

 lying between the epi- 

 gj'num (ep) and gills (gi) 

 and the spinnerets (sp) ; 

 pits or dimples may also 

 be seen on the venter 

 s_vra metricalh^ arranged 

 as on the dorsum. The 

 median venti'al Ijand is 

 A „ ^x, .v,„ !>,=.,.. usuallv bordered by a 



Abdomen and Parts. ^ J 



Fig. 93. Dorsal view; pd, pedicle uniting to cephalothorax ; ba, base or Strip 01 llgllter COlOr 



fore part; d.co, dorsal cones or shoulder humps; fol, folium or dorsal )iTf)T.p qj. Ipee broken 

 pattern ; ap. apex ; sp, spinnerets ; pt, pit marking inseiiiou of muscles ; 



mn, median line of dorsum. Fig. 94. Side view ; vn, venter ; ep, epi- When thc abdomen is 



gynura ; gi, breathing gills ; other references as above. tllickcned at tllC apCX, 



the space between the dorsal and ventral apex is known as the apical 

 wall of the abdomen. On either side or shoulder of the dorsal base some 

 species have conical prominences known as dorsal cones or tubercles (d.co). 

 These are sometimes placed at several other points, usually along the mar- 

 gin of the dorsvim. In some species these are hard and spinous. 



The exterior parts of the epigynum referred to in the description are 

 illustrated at Figs. 95, 96. The atriolum vulvse, or vulval porch, is a 

 vaulted porch or hood that curves over the genital opening, in 

 front of which (anterior) it is located. It is usually chitinous, 

 and covered at the base witii hairs. The middle part in many 

 species is prolonged into a .shaft or scapus atrioli, which is sometimes a 

 mere flap, and again is much lengthened. Sometimes it is smooth, some- 

 times wrinkled or rugose, often with a row of stout hairs thereon. Fre- 

 quently it is grooved or hollowed along the under surface. The tip is 

 more or less attenuated and rovmded, or sometimes pointed ; in many 

 species it is widened into a bowl or spoon, usually oval, but sometimes 



Epigy- 

 num. 



