IN CERTAIN LEPLDOPTERA. 283 



The scaphium is very difficult to understand without dissection, to which I have been 

 reluctant to resort with so valuable a species, contenting myself with careful study of 

 the parts in situ. It seems to me, after much consideration, that the scaphium proper 

 is reduced to a slender " boat " running off to a point under the tip of the uncus to which 

 it seems attached, above the triangular basal expansion, by fibrous processes on each 

 side. I can see nothing answering to the ordinary " double teeth." The keel, on the 

 other hand, seems to be unusually developed into the large bagging body which hangs 

 below *. 



In the lower part of the cavity is seen the penis — here a moderately thick column of 

 polished brown chitine which projects almost horizontally from the abdomen to the 

 edge of the valve, and terminates in a long drawn point, just before which it sends 

 off two expanded foliations on the upper side (the organ being reversed), which are of 

 thinner substance than the tube, and which face each other. 



Towards the base of the genital cavity, projecting from one of the lower dilatations of 

 the scaphium, I find, in the forms of this species, particularly distinct in 0. Richmondia, 

 two short sharp polished spines on each side of the penis, so placed that the four are in 

 a line with it. I cannot suggest the use of them ; their position seems to preclude 

 prehension. 



Obnithopteba pbonomus, G. R. Gray. (Plate XXVI. fig. 4.) 



The harpe is not distinguishable from that of 0. Arrucma, except that the armed disk 

 is a little wider. In removing the valve, the harpe detached itself, together with a 

 portion of the lining-membrane, so that I could lay it, quite alone, on a glass slide 

 for the stage of the microscope. The black shining teeth are about fifty in number, 

 arranged exactly as in Arrucma, and interspersed with stout bristles or straight spines, 

 all projecting at nearly a right angle to the plane of the stem. The teeth are some larger 

 than others, irregularly crowded, decidedly curved, stout, pointed, black, glittering in the 

 light; the chitinous substance of the disk and stem translucent, gall-yellow by the 

 transmitted light, varying in depth of tint, according to the thickness, and, as I think, 

 according to the density, of the material. 



The uncus differs much from that of both the preceding and succeeding forms. It is 

 rather short, not uniformly curved, but bent down near its middle with a kind of knee ; 

 it widens rather rapidly to the base ; and the vertical rami, which I will call the keel of 

 the uncus, increase in depth rapidly. The uncus is not why. 



I could find not the least trace of a scaphium, in the single specimen that I examined. 



The penis, reversed, was abruptly inclined from near the base downward ; so that 

 it lay in the very angle between the valves, and was so long that the tip was fully 

 seen without, pointing obliquely towards the head of the insect. The expanse of the 

 lips was empty to a considerable depth ; the median line channelled beneath, as if the 

 integument there were thin, and had contracted in drying. 



* Since the above was written I have made examination of the specimen in another mode. Having softened the 

 parts by moisture, I stretched them apart with needles, and thus satisfied myself that my explanation hazarded 

 above is the true one. 



10* 



