^2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 82 



epistoma by a faint suture. A pair of bristles and two punctures 

 occur near the basal margin. The setae are called setae clypei. 



Labrum. — The labrum (fig. 37, Lar) is basally separated from the 

 clypeus by a distinct suture. It consists of a heavily chitinized half 

 circular plate. It is as long as, and about one-third narrower, than 

 the clypeus and bears several papilla apically. Half way of its length 

 occur two long bristles, the setae labralis. 



Epistoma. — Between the front and the clypeus, a narrow thickened 

 transverse band occurs which may be designated as the epistoma 

 (Est). Laterally this structure is slightly bent forward and this 

 part bears the dorsal articulation of the mandibles. On the latero- 

 basal angles, near the suture, a long bristle is situated. The proposed 

 name is seta epistomalis. 



Pleurostoma. — A faint suture hems the lateral portion of the oral 

 foramen, parallel to the lateral exposed part of the mandibles, which 

 cuts off a narrow area of the cranium. This area, the pleurostoma, is 

 slightly raised externally; internally it is ridgelike, and connects the 

 epistoma with the hypostoma. 



Hypostoma. — The hypostoma (fig. 37, Hst), which bears the ven- 

 tral articulation of the mandibles, is rather ill-defined externally. In- 

 ternally it is ridgelike and the articulatory condyles and fossa are 

 submerged. Towards the occipital foramen it is extended in another 

 ridge from which the connecting membranes of the maxilla and the 

 submentum arise. 



Occipital foramen. — The occipital foramen (fig. 6, Oct) is situated 

 on the caudad face of the head capsula. It is heart-shaped and is bor- 

 dered by a ridgelike rim, the occipital apodeme (fig. 37, OcA). The 

 latter is interrupted ventrally. The entogular plate extends into the 

 foramen under the occipital apodeme giving the open space of the 

 foramen the shape of a triangle, the sides of which are broadly 

 rounded. 



Gtda. — The gula (Gu) is present as two small lobes, each situated 

 along the ventro-lateral angles of the occipital apodeme. The lateral 

 limitation is indicated by an obscure suture. 



Entogular plate. — A subchitinous plate (Eg) connects the genal 

 areas and extends ventrally up to the hypostoma. It was called the 

 entogular plate by Hopkins. The open space of the oral foramen is 

 also reduced by the lammella-like extension of this plate. The entogu- 

 lar plate is not visible externally but hidden from the submentum. 



Pregena. — A narrow area along the ventral extensions of the hypo- 

 stoma, and laterally limited by obscure lines, may be considered as 

 the pregena (Pr). 



