206 Zoologica: N. Y. Zoological Society [111:7 



the buccal membrane above labium and above the mental- 

 submental area ; consisting of a median broad and short, 

 slightly chitinized, transverse tentorial bridge {ten. b. Plate 

 VII, fig. 7), situated a short distance above gular plate 

 and of two pairs of tentorial arms ; the first pair of arms 

 lateral {t. I. a. Plate VII, fig. 7), between bridge and tentorial 

 pits {tp. Plate VII, fig. 7) where gular plate and epicranium 

 meet; the second pair anterior {t. a. a. Plate VII, fig. 7), reach- 

 ing from tentorial bridge toward the dorsal side of cranium, 

 their external ends distally indistinct. Ocelli (Plate VIII, fig. 10) 

 six, placed in two groups, a lower behind mandible and an upper 

 straight behind antenna and right above first group. Antenna 

 with large basal membrane, two- (three-) jointed; basal joint 

 (i Plate VII, fig. 5) short, second joint {2 Plate VII, fig. 5) long, 

 claviform, with tip (3 Plate VII, fig. 5) more or less distinctly 

 separated as a small additional joint. Mandible (Plate VII, figs. 

 4 and 5) with molar part, retinaculum and accessory ventral 

 condyle ; half as long as head ; apical part (p. sc. Plate VII, fig. 5) 

 distinctly constricted, incurved, vertically compressed, fornicate, 

 cleft with some toothlike ends ; rest of mandible horizontally flat, 

 subtriangular with wide base; retinaculum present (;• Plate VII, 

 fig. 5), hamate, short, pointed, with enlarged socket; molar part 

 broad (m. Plate VII, fig. 5, Plate VIII, fig. 17), compressed, with 

 dorsal surface smooth, ventral surface roughened by numerous 

 granules, these being anteriorly rather large and irregularly dis- 

 tributed, posteriorly minute and densely placed in longitudinal 

 rows; basal molar fringed with a series of anomalous, chitinous, 

 stiff, filamentous processes (fit. pr. Plate VIII, fig. 17), which 

 gradually diminish in length from inner corner of basis toward 

 accessory condyle; accessory condyle {acces. Plate VIII, fig. 17), 

 as mentioned above, fitting into groove {fos. a. c. m. Plate VIII, 

 fig. 16) in fifth hypopharyngeal rod.* Ventral mouthparts 



* This articulation between the mandibles and the whole system of 

 amalgamated chitinous hypopharyngeal and epipharyngeal structures indi- 

 cates that the side to side movements of the mandibles caused by extensor- 

 flexor — (^abductor-adductor) — muscles, always must be coincident with 

 the forward-backward movements of the following closely united structures: 

 the anterior portion of oesophagus, the hypopharynx with other buccal 

 structures, and the ventral mouthparts, and also coincident, when a free, well- 

 developed labrum and movable clypeus are present, with their up and down 

 nodding motions. All forward and upward directed movements are caused 

 by blood pressure combined with special arrangements of the articulations; 

 all backward and downward directed movements by retractor muscles. 



