NO. 13 STAPH YLINIDAE — BLACKWELDER 1 7 



bearing a pair of large setae on each side. The prementum arises from 

 the inner or dorsal surface of the mentum. It is much narrower than 

 the latter and roughly square in outline. Its distal end is expanded 

 into two pairs of lobes, an inner pair of glossae and an outer pair of 

 paraglossae. The glossae (ffl) lie on either side of the median line, 

 fused throughout their length except at the tip, which is slightly 

 notched. They are ordinarily visible between the labial palpi (//>) 

 on the ventral aspect. The paraglossae (pgl) are expansions of the 

 anterolateral corners of the prementum. They are more distinctly 

 produced than the glossae, but are almost always hidden behind the 

 first segment of the labial palpi (Ip). Both the glossae and the para- 

 glossae are membranous, unpigmented, and translucent. They have 

 no vestiture with the exception of a few scattered hairs on the anterior 

 margin between the glossae and the paraglossae. The prementum bears 

 on each side at its median lateral margin a large imperfectly differenti- 

 ated lobe, the palpiger (pig) which bears the labial palpus (Ip and fig. 

 2 B) on its distal end. There is a single stout seta at approximately the 

 base of each palpiger. The labial palpus is three-segmented with the 

 first two segments nearly equal in size and the terminal one somewhat 

 elongated. This palpus differs from the maxillary palpus in being 

 devoid of setae, except for a very few long hairs. The extreme tip 

 of the third segment is slightly emarginated and bears a small median 

 area of what appear to be sensory papillae (fig. 2 C, senp). The sur- 

 face of the tip is also set with relatively very large pores {p), with 

 a few of what appear to be minute canalicuH {can) ending at the sur- 

 face in a small, dark dot. 



On the inner or dorsal surface of the labium is a large appendage, 

 the hypopharynx (fig. 2D). This arises from the region between 

 the mentum and submentum and the mouth opening, and bears two 

 slender lobes distally. These lobes extend in a narrow V-shape be- 

 hind the paraglossae of the labium and are armed along the inner 

 edge with a comb of long stout setae. This entire organ is very 

 membranous and translucent, and the distal portion is covered with a 

 very dense vestiture of short fine hairs. It is so exactly beneath the 

 labium (that is, dorsal to it) that the tips of the comb-bearing lobes 

 appear to be the paraglossae of the labium, even in dissections. It 

 is firmly attached to the ental surface of the labium. 



THE TENTORIUM 



Each half of the tentorium or internal skeleton of the head is com- 

 posed of a posterior arm (fig. i F, pta) , an anterior arm {ata), and 



