302 ME. P. H, GOSSE ON THE CLA8PING-ORGANS 



arrange this vast genus in naturally allied groups — J expected to have here another 

 example of abnormality, such as we see in the Polydorus group. But, except that the 

 uncus is abruptly bent perpendicularly downwards, as it is in P. Hector, the organs are 

 of the usual type, though peculiar in detail. 



The valve is small, semioval, the outline slightly bulging dorsally and fringed only with 

 a few very minute hairs. The interior is almost level for a wide space within the ventral 

 margin, then abruptly descends with a deep cavity, which extends close to the dorsal 

 margin ; internal surface cloth-like, nearly black. Within this cavity lies a great scmi- 

 crescentic harpe of shining chitine, its lower half divided off into a kind of stem, the whole 

 somewhat like a butcher's cleaver with its handle, and all springing from a dilated base by 

 which it is affixed to the proper knob, within the bottom of the 8th segment, apparently 

 distinct from, though in close proximity to, the conjunction of the valve itself with the 

 segment. By removing the harpe, which is very readily separated, we see clearly (what 

 is, indeed, discerned by the aid of a pocket-lens, even in situ) that the straight side, or 

 what answers to the cutting-edge of the cleaver, is serrated with sharp teeth, some- 

 what irregular both in size and arrangement ,*. 



The abdominal organs (fig. 13) are remarkable for the abrupt deflection of the uncus 

 (perhaps accidental), the extreme minuteness of the scaphium, and the great development 

 of the penis, which is reversed. 



Papilio Machaox, Linn. (Plate XXIX. figs. 14-16.) 



In our own familiar Swallow-tail the calve is of the ordinary subtrigouate outline, 

 with a rounded point. Externally it is clad with a close dense coat of pale-yellow scales, 

 which do not project beyond either margin ; there arc, however, black hairs, growing 

 from the interior, more than usually stout, long, and close, along the dorsal side, and 

 forming a produced point. These crowded hairs, the whole cavity being of a sooty 

 brown hue, effectually conceal the marginal line on that side. 



A low pale ridge runs through the valve along its central line, which does not seem 

 connected with the harpe. Just within the ventral margin, following its line from base 

 to tip, runs a plate of glittering black chitine, fixed to the floor by one edge, while the 

 other is free, and leans over towards the dorsal side. At mid-length its height abruptly 

 increases ; and thence to the point it is a keen knife-blade, only cut into minute sharp 

 teeth, about a score in number, exactly like a saw. This harpe is of chitine so dense as 

 to appear quite black, but transmitting a rich translucent golden-brown hue when 

 viewed against the light, except a slender line just below the teeth, which is considerably 

 paler, as if there were a band of less density just there, or possibly a groove, though 

 it is not a place at which one would expect the structure to be weakened. 



The shining chitinous material is spread widely over the valve-cavity as an exceedingly 



As a rule, I content myself with delineating one of the valves. Bui of P. Ar/avus I have given the left as well 

 as the right. In the course of examination this left valve came away, leaving the harpe still attached to the segment. 

 When 1 detached this, in turn. 1 observed what appeared an accessory piece behind the blade, and following a similar 

 curve; this I delineated as 1 saw it, without understanding it (see fig. 12.) Eeplacing the harpe in the valve, 

 I drew- it, as I supposed, in situ, as at fig. 11 ; but, afterwards, having detached the right valve and its harpe entire, 

 I saw nothing of this additional piece ; I therefore conclude that it is a piece torn off accidentally from the back of 

 the harpe. 



