166 PROCEEDINGS OF THE ACADEMY OF [1898. 



The trans-frontal vary in Dumber in different species, in the two 

 sexes of the same species and even in different individuals of the 

 same sex. In the female they are directed mesad and cephalad 

 across the frontal vitta and more or less of them may decussate with 

 their fellows of the opposite side. In the male they are generally 

 more numerous than in the corresponding female, and they are 

 directed cephalad with (usually) a curve dorsad or ventrad. As 

 in the female they may decussate, but as a rule they do not. 



Each geno-vertical plate is continued over the vertex to the occi- 

 pital surface in the form of a little ridge. This ridge is bounded 

 laterad by a suture which begins at the dorso-mesal angle of the eye, 

 runs to the vertex, over the vertex to the occipital surface of the 

 head, and then in a ventro-mesal direction as far as the great cen- 

 tral foramen. About half way between the vertex and the great 

 foramen the little ridge bifurcates. The lateral branch continues 

 in about the same direction as the main ridge, while the mesal branch 

 runs more or less directly mesad and joins its fellow of the opposite 

 side ; thus by these two little ridges and their mesal branches a tri- 

 angular area is marked out at the dorso-central part of the occiput. 

 At the very beginning of each of these little ridges just mentioned, 

 right on the vertex, stands a bristle which is called the inner verti- 

 cal, and down a little way on each ridge just before it bifurcates 

 stands another which I propose to call the oceipito-central. Both 

 of these bristles are present in every species that I have so far had 

 the opportunity of examining. They vary in size in different spe- 

 cies and in the two sexes of the same species. The inner vertical 

 project dorsad with more or less of a curve caudad and mesad, so 

 that they sometimes decussate a little and are almost always con- 

 vergent. The amount of convergence varies even in individuals of 

 the same species and sex. The oceipito-central project dorsad and 

 mesad sometimes with a curve, sometimes without a curve, some- 

 times decussating a little with one another, sometimes apparently 

 decussating with a bristle called the post-vertical, which will be de- 

 scribed later. 



On the vertex, just laterad the beginning of the little ridge and 

 the inner vertical bristle, stands a bristle which is called the outer 

 vertical. This bristle varies much in size in different species and in 

 the two sexes of the same species. It is larger in the female than in 

 the male, and is absent in the males of some species although pres- 

 ent in their females. 



