AND MOUTH-PAKTS OF CHLOROPS TiENIOPUR. 405 
the appearance of being sense-organs. The dorsal surface of the labrum is 
strongly convex from side to side ; its base articulates with the distal ends of 
tlie stipites (fig. 6). The labrum, together with the epipharj-nx, is easily 
lifted from the surface of the proboscis and rotated dorsally, its b:i-e hinging 
on the stipites. 
The Vertex "is interpreted as including all the cephalic and dorsal 
aspects of the epicranium except the front. . . . The region of the vertex 
ventrad and mesad of each compound eye is a gena " (Peterson^ pp. 23-22). 
It is only necessary to remark that what Peterson calls the front is, in my 
opinion, part of the vertex. The term "front" as applied to Cyclorrhapha 
has no true morphological significance, but the region defined by the term is 
so well understood, and tlie term is so constantly used in taxonomical writings 
on Diptera, that it would, I think, be a mistake to propose any new name for 
this region. 
The Compound Kijes and Ocelli. — The only noteworthy feature concerning 
the eyes is the [)resence round their margins of a well-marked, though 
incomplete, ocular sclerite (figs. 1 & 2, o.s.). This ring sclerite is incomplete 
anteriorly ; it bears two small peg-like projections, an antero-ventral (a.p.) 
and a postero-dorsal (p.p.). The three ocelli iire situated on the vertex some 
distance dorsal to the frontal suture, and lie on a raised and dark-coloured 
triangular aiea (fig. 2, o.i.), which is continued forwards in front of the 
median ocellus as a dark-coloured internal chitinous ridge running along tiie 
median line of the vertex and ending at the dorsal margin of the frontal 
suture. 
Occiput and PosTGENiE. 
Owing to the absence of sutures on the caudal aspect of the head (fig. 2), 
it is not possible to define with certainty the limits of the occiput and post- 
genre, and accordingly Peterson's view is followed that all regions of the 
caudal aspect lying dorsal to a transverse line drawn through the middle of the 
occipital foi-amen belong to the occiput, while the areas ventral to this line 
and lateral to the mesial membranous area are the postgense. The dorsal half 
of the foramen is strengthened by a thickening of the occiput (p.o.) which 
provides articulation for the neck scleiites. I follow Peterson in calling this 
the Parocciput. It is not marked off from the occiput by a secondary 
suture, as is frequently the case in Diptera. On each side a chitinous peo- 
(li.t.) projects mesially across the foramen, the two almost meeting in the 
median line and dividing the foramen into dorsal and ventral halves. These 
certainly appear to me to be processes of the ventral ends of the parocciput, 
but Peterson has named apparently identical structures (e.c/. in Chlornpisi'a 
glahra, fig. 132) as the body of the tentorium, and as he has examined a 
large series of forms and has therefore had the opportunity of tracing the 
variation of tlie body of the tentorium in Diptera, I have decided to follow 
