4 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.65. 



caudad of this ridge, named collum (co, fig, 8) is strongly deflexed. 

 The genae {ge, figs. 5 and 14) include the greater part of the epi- 

 cranium on the ventral aspect of the head. They extend from the 

 occiput cephalad to the postgenae, laterad and dorsad to the vertex, 

 and meet on the meson. The postgenae {pge, figs. 5 and 14) include 

 the ventral and lateral part of the epicranium ceplialad of the 

 genae. They extend from the genae to the cephalic margin of the 

 head capsule, laterad to just beyond the ventral articulation of the 

 mandible, and mesad to the hypostoma and the attachment of the 

 cardo. The cephalic margin is inflexed and produced as a triangular 

 projection between the mandible and maxilla, where it joins with the 

 ventral part of the clypeus. 



The hypostoma {h, fig. 14) is a paired structure and consists of a 

 V-shaped area mesad of the postgenae on the ventral aspect of the 

 head. Its caudal extent is indicated by a short, dark, transverse bar, 

 which is about one-third the distance to the caudal margin of the 

 head. This transverse bar is the point of attachment of the caudal 

 arms of the tentorium. The maxillae and labium are attached at 

 the cephalic margin of the hypostoma. 



The fronto-clypeo-labral area {fcla^ fig. 8) is between the frontal 

 sutures and extends cephalad to the cephalic margin of the head. 

 It consists of the frons, clypeus, and labrum. The sutures separat- 

 ing these sclerites are obsolete. The frons (/, fig. 8) is between the 

 frontal sutures and is considered as extending cephalad to the ceph- 

 alic margin of the small sclerite, the " latero-clypeus," mesad of the 

 antennae. Its cephalic margin is determined by the point of attach- 

 ment of the anterior arms of the tentorium. There is a \}-slhaped 

 ridge {us, fig. 8), bearing two setae, on the caudal part of the frons. 

 The clypeus (c, fig. 8) is considered as extending cephalad from the 

 frons to just cephalad of the tooth-like projection on the cephalo- 

 lateral angles. Each lateral one-fourth of the clypeus, named " an- 

 gyjlus frontalis " by Schiodte, is raised above the mesal part («/, fig. 

 8). The ventral surface of the clypeus is strongly joined to the 

 postgenae ventrad of each tooth-like projection. The lahrum, form- 

 ing together with the cephalic part of the clypeus the " iiasale " 

 (Boving), is folded back on its ventral aspect to the epipharynx 

 (figs. 7 and 8). The small, rectangular sclerite (/«?, fig. 8) mesad of 

 the antenna is considered as a lateral sclerite of the clypeus. For 

 this sclerite I propose the name of " latero-clypeus.''^ 



The tentoinwm or internal head skeleton, consisting of the anterior, 

 dorsal, and ventral arms, is not strongly developed. Eiu-h anterior 

 arm {aat, fig. 7) is attached along the suture separating the latero- 

 clypeus from the clypeus and, at its cephalic end, is produced into a 

 knob-like projection to which the dorsal acetabulum of the mandible 

 articulates. Each anterior arm projects ventro-mesad until they 



