140 



while the labrum is strongly narrowed upward (e.g. H. nasutus, 

 mihi), this structure is very conspicuous ; while in some whose 

 clypeus is but little emarginate, while the labrum is feebly curved 

 above and feebly elevated (e.g. H. dehilis, miJii), the outline of the 

 head from the most favourable point of view, — which is a point 

 whence the sight is almost parallel to the surface of the head, — 

 is a curve in which the sinuations are little noticeable. In 

 order to compare the lobes of this " trilobed outline " in definite 

 terms, I call the length of a straight line joining the extremities 

 of the free outline of each lobe the " width " of that lobe, and by 

 the "length "of the lobe I mean the distance that it projects 

 outward from that line. 



To minimise words in the following descriptions I call the 

 fringe of stout hairs running along the sides of the elytra 

 " normal," when it is not continued in any markedly conspicuous 

 manner round the apex. 



It should also be noted that whenever the " length " of the 

 metasternum is referred to, its length is to be measured along the 

 suture between it and its episternum. 



The hind angles of the prothorax as seen from above are in 

 many cases not the real angles formed by the meeting of the 

 lateral and posterior reflexed margins, and consequently they 

 present different appearances from different points of view. To 

 meet this difficulty I have in every case described the hind angles 

 of the prothorax as they appear from directly above the middle 

 longitudinal line of the insect, selecting in the line thus indicated 

 the point from which the angles appear most strongly defined. 



Tabulation of the groups of Heteronyx thus far dealt with, 

 inclusive of those in the present memoir : — 



Section I. — Clypeus altogether above the summit of the labrum 

 (as in most other Melolonthidse). Vide P.L.S. N.S.W. (2) III., 

 p. 1328. 



Section II. — Intermediate forms, — in which the labrum is 

 turned upward, and nearly or quite rises to the level of the plane 

 of the clypeus, but does not overtop it (Ix. p. 1353). 



