56 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 1 10 



ward below the large basal segments. The venom gland of each 

 appendage is an elongate, cylindrical sack (fig. 19 A) lying in the 

 upper part of the basal segment. It is covered by a layer of flat, 

 strongly striated muscle fibers, which go obliquely upward and pos- 

 teriorly on each side, and their ends overlap along the midventral 

 and middorsal lines. The duct traverses the fang to open by a pore 

 (VPr) near the tip on the convex surface. 



Beneath the chehcerae, the labrum (fig. 18 A, Lm) projects from 

 the anterior wall of the prosoma in the form of a large, soft lobe 

 with two small lobules on the angle between its short dorsal surface 

 and the long, receding anterior surface. The sides are compressed 

 (B) but expanded below to form before the mouth an upper lip 

 fitting snugly into the concavity of the under-lip sternum (A, IIS). 

 From the base of the dorsal surface of the labrum there is reflected 

 upward in the body wall beneath the chelicerae a small, transverse 

 epistomal plate (B, Epst) with prolonged lateral angles. The sternum 

 of the pedipalp segment (A, IIS), which, as in all the Araneida, 

 constitutes the under wall of the preoral cavity, is a small plate 

 detached from the large sternal plate of the leg segments. As just 

 noted, its concave upper surface receives the expanded lower end of 

 the labrum. 



Between the under surface of the labrum and the pedipalp sternum 

 is the short preoral food cavity (fig. 19 B, PrC), which leads directly 

 through the mouth (Mth) into the lumen of the pharynx (Phy). 

 The pharynx slopes steeply upward behind the labrum and epistome, 

 and the oesophagus (Oe) dips downward from its inner end. The 

 walls of the pharynx are formed of an inwardly convex dorsal plate 

 (dpi) and a concave ventral plate (vpl) united along their edges by 

 membranous conjunctivae. The strongly sclerotic dorsal plate (C) 

 is continued from the under surface of the labrum (Lm), the larger 

 but weaker ventral plate (E) from the upper surface of the deuto- 

 sternum (IIS). The dorsal plate (C) presents a high, rounded 

 median lobe, flanked by two narrow lateral lobes. The middle lobe 

 is deeply incised at its inner end, but a median arm is continued 

 through the emargination. Traversing the middle lobe from the 

 end of the arm almost to the labrum is a median channel (C, D, dc) 

 with strongly sclerotic walls. At its upper (posterior) end the channel 

 is widely open before the mouth of the oesophagus, but along the arm 

 of the plate it is nearly closed by lateral folds of membrane, and then 

 becomes again an open groove that tapers to a narrow slit ending 

 shortly behind the labrum. On the dorsal plate of the pharynx is 



