22 RKVI.SIOX OP THE AMTCTERIDESj Vl., 



ridge connecting the inner surfaces of tlie tubercles or crests which rise above 

 the ejes. This ridge, wjiich will be termed the intercristal ridge, varies in de- 

 velopment and is obsolete in some species, while in one section of the genus it is 

 absent, and the division between the head and rostrum is marked by a transverse 

 impression or sulcus. The supraorbital crests, which arise on cither side above 

 and somewhat in front of the eye.-;, show great variation in shape and development, 

 the differences being of decided specific value. As a rule these crests are com- 

 pound, consisting of two more or less closely united portions, which I have in 

 general termed branches or rami, the po.sterior of which is almost always pointed. 

 A few species show three distinct branches, generally, however, only separate at 

 the apices. The branches vai-y much in form and development ; sometimes they 

 are more or less obtuse or dentifoiTn, sometimes forming acute spines resembling 

 the branching antlers of a deer. In otlier species again, the two portions cannot 

 be made out, the crests consisting of a single tubercle or spine. The relation of 

 the intercristal ridge to the supraorbital crests appears to differ somewhat in 

 different gi-oups; in .-1. tridentatus and one or two others, the ridge joins the crests 

 at the base of the median portion; in certain of the bidentate species the con- 

 nection is clearly with the anterior portion, but in otliers apparently with the 

 posterior. In many species, however, the crests arise, from a comparatively nar- 

 row base into which the ridge runs, and its continuity appears to be with either 

 the posterior or anterior portion, according to the position from which it is 

 viewed. I have not, therefore, been able to make as extensive a use of this 

 character in separating groups of species as I had hoped. In some groups the 

 base of the crests extends for quite an appreciable distance behind the inter- 

 cristal ridge, in others to a mucli less extent. On the outer side of the head, in 

 front of the eye, is a deep groove ; this generally extends for a short distance on to 

 the outer surface of the crests. In the species where the rostrum is separated from 

 the head by a transverse sulcus, this is generally continued for a short distance 

 on to the inner surface of the crests. The rostrum in AcantholvphuK is always 

 more or less excavate above, with the external margin generally raised and 

 often bearing a distinct tubercle or spine. At the base are two more or 

 less convergent ridges, joining the intercristal ridge; these are often 

 obscure or obsolete. The spaces between these ridges and the lateral margins I 

 have termed the basal foveae; they are generally deep and closed around their 

 margin, but sometimes the external portion of the margin is interrupted. The 

 antennae are long and comparatively slender; the two basal joints of the funicle 

 are longer than the othere, but vary in their com])arative Icngtlis; the true length 

 of th(! first joint can only be seen when viewed obliiiuely from behind. Tlie club 

 varies in length and thickness ; in mimy species the basal portion is attenuated, 

 and I have used the teiin pedunculate to describe such forms. 



The prothorax shows great variation in structure, but tlie widely explanate 

 upper surface with strongly dentate or tuberculate lateral margins is practically 

 characteristic of the genus. One of the characters ui)on wliich I would divide the 

 genus into two sections is the form of the anterior margin; in the majority of 

 species this niargin is widely rounded above and slightly produced, with an evi- 

 dent sinuation on each side leading to the fomiation of a wide and little prom- 

 inent convexity below con-esponding to the ocular lobe; in the species forming the 

 second .section, the margin is tnuicate or subtruncate above, and there is no sinu- 

 ation nor corresponding ocular lobe. The disc of the prothorax is cro!?sed Ify 

 three, more or less distinct, transverse impressions or constrictions, of which the 



