IN CERTAIN LEPIDOPTEliA. 337 



The falling curtain of the scaphium-base forms below its middle an enveloping sheath 

 for the penis, which sheath then runs back around it to the very origin of the organ. 

 This sheath is close, yet wholly free, allowing independent action to the penis, while 

 it is attached on each side, by a slender ligament, to the floor of the cavity. 



Tracing back the organ to its origin, we see that it is fastened by muscles to a thin but 

 wide ridge of chitine, that springs from the bottom of the seventh segment, and stands up 

 erect transversely, yet considerably hollow, the concavity backward. This, I presume, 

 gives the point of resistance for the retraction of the organ after coition. The penis, 

 behind this attachment (/. e. thoraxwards) enlarges into a thick and long fleshy bulb, 

 which seems free in the hollow of the sixth segment, and bends back upon itself. 



The eighth segment at its bottom gives rise to a hollow shell-like plate of firm polished 

 chitine, much larger than that of the seventh just mentioned. This and its fellow form 

 the floor of the genital cavity, surrounding and closing the bases of the valves. To the 

 upper edge of this plate the penis is affixed by a muscular or tendinous cord stretched in 

 the contrary direction to that of the seventh segment. I conjecture that this projects 

 the organ in coition, as the former retracts it, and that both limit its action to the 

 median line of the body. 



Hinge-knobs. Within the plate last described, nearly close to it, and nearly parallel 

 with it, but quite free from it, is that curious piece, on each side, which I have called a 

 knob, but which (here, in Remus, certainly) is hollow — a very firm and stout chitinous 

 shell, to which the vcntro-basal edge of the valve is closely articulated, and from which 

 the root of the harpe springs. 



The small italic letters denote : — a, the uncus ; b, the chitinous lamina of the sca- 

 phium ; c, its cheek ; d, the sulcus ; e, the aristae ; /, the pentagon ; g, the keel ; h, its 

 lobes ; i, its groin. 



I add some results from late examinations of a few species of Papilio, as chiefly 

 shedding light on the structure and relations of the scajfliiutn. 



P. Ascalaphus. The uncus, scaphium, curtain, and penis, can all be resolved into the 

 Remus type. The cheek, instead of being erect, leans horizontally outward, making the 

 sulcus much broader ; the front edge of the cheek is diminished to a slender acute tooth 

 of black chitine; and its hinder portion (= the sulcus side in Remus) is here the semi- 

 globose " boat-gunwale " of brown chitinous membrane, or thin horny plate, so corru- 

 gated as to make strong oblique ridges, sloping inward and forward, on each side of the 

 shallow sulcus. The keel, though somewhat changed in form, seems homologous ; but 

 the pentagon appears quite wanting. 



In P. Mayo, and in P. Memnon, the general structure is the same ; the differences of 

 detail are slight and unimportant. 



P. Agamemnon. The back of the upper part of the scaphium is elevated, skull-like, 

 and is thickened into a ridge, where the under surface of the imcus-base is attached to it, 

 I think, organically, as may be seen when the uncus is forced off. This ridge descends 

 obliquely on each side, and forms the lateral margin of the curtain, reaching below the 



SECOND SERIES. — ZOOLOGY, VOL. II. 47 



