EXTERNAL ANATOMY OF INSECTS. 4.29 
process of a similar structure at each of the dorsal angles 
of the base of the mandible, the intermediate one being 
wanting ; and the articulation does not materially differ, 
as far as I have examined them, in the Hymenoptera and 
Neuroptera. In the Orthoptera, the structure approaches 
more nearly to that of the stag-beetle, since there are 
three prominences: it is thus well described by M. Mar- 
cel de Serres: “ This articulation,” says he, “ takes place 
in ¢wo ways. At first, in the upper surface of the man- 
dible, and at its base, may be observed two small promi- 
nences and a glenoid cavity ; these prominences are re- 
ceived in two glenoid cavities excavated in the shell of 
the front, as the cavity of the mandible receives a small 
prominence of the same part. Below the mandible, and 
at its base, there is a kind of condyle, which has its play 
in a cotyloid cavity excavated in the shell of the temple, 
far below the eye, and at the extremity of the coriaceous 
integument of the head?.” Within the head in this 
Order, at least in Locusta, is a vertical septum which 
divides the head into two chambers, as it were, an occi- 
pital and a frontal, consisting of a concave triangular 
stem, terminating in two narrower concave triangular 
branches, so as to resemble the letter Y, and forming 
three openings, an upper triangular one, and two lateral 
subquadrangular ones, which last are the cavities that re- 
ceive the base of the mandibles. This partition, which 
I would name Cephalophragma, doubtless affords a point 
of attachment to many of the muscles of the head. It 
does not appear to have been noticed, unless it be syno- 
nymous with the zntermazillary arcade of Marcel de Ser- 
* Comparaison des Organes de la Mastication des Orthoptéres, 2. 
