W. H. FURLONGE ON THE PULEX IRRITANS. 197 



leaps. The strengthening of the plates, by the marginal deposit of 

 additional material spoken of above, receives, in this segment, a 

 still further development, and, for the purpose of giving yet greater 

 solidity to the parts, stout transverse ribs or braces of chitin, at 

 intervals, unite the anterior and posterior margins of the plates. 

 In the meta-thorax, indeed, though, in fact, formed of three plates, 

 like the two anterior segments, these are so firmly united or fused 

 together, as practically to constitute one very strong plate, embrac- 

 ing the back and descending on each side, somewhat below the 

 medial line, terminating in rounded sockets, the margins being 

 surrounded, or nearly so, by strong rings of dark brown chitin, to 

 the external edges of which, at the point of junction with the ver- 

 tical band of chitin, the legs are attached. Afi in the first and 

 second segments, the superior plate of the meta-thorax is united 

 to the underlying skin by the anterior half only, and it would 

 appear, as if the posterior vertical band of chitin is imbedded in the 

 skin and forms the line of attachment of the plate to it, the posterior 

 half overlapping and playing freely over the first segment of the 

 abdomen. Three rows of setee emerge from the meta-thorax, the 

 anterior set from the middle line of the plate, the posterior row 

 from its edge, and the third row is placed exactly between them. 

 Each row contains about twelve hairs. 



We now arrive at the description of — 



The Legs, six in number, and carried, as before stated, in pairs, 

 on each segment of the thorax, and attached to them in the manner 

 already described. The anterior pair of legs is the smallest, the 

 posterior pair considerably the largest and longest, but they are 

 all composed of the same number of joints, which are arranged in 

 a precisely similar manner. They consist of — 



1. The Coxa, which in the flea is unusually large, and in fact 

 constitutes the most important and powerful joint of the leg. 



2. The Femur. 

 2. The Tibia. 



4. The Tarsi, consisting of five joints, of which the upper is 

 much the largest, the terminal joint carrying a pair of Jong, curved 

 claws, which are capable of contraction, and spring from a soft pad 

 studded with short hairs. The external surfaces of the legs are 

 abundantly furnished with stiff setse, of which the thickest and 

 longest spring from the posterior margin of the tibia?. 



The flattened tubular joints composing the legs, are closely 



