1872.] DR. LE CONTE ON PLATYPSYLLI D,E. 801 



a faint triangular longitudinal impression is also seen inside of the 

 humeri ; five dorsal segments of the abdomen, and the angles of the 

 one anterior to them, are exposed. Lower wings wanting. 



Abdomen : dorsal surface flat, not margined at the sides, each 

 exposed segment with a transverse row of small depressed bristles ; 

 spiracles situated near the hind angles of each segment, equidistant 

 from the lateral and posterior margins ; ventral segments slightly 

 convex, six are visible behind the posterior coxse, which conceal two 

 segments and the base of the third. The ventral sutures are straight, 

 with the exception of the last two, which are curved ; the last seg- 

 ment is feebly bisinuate at tip. 



Coxse flat, not at all prominent ; front ones small, subtriangular, 

 with rounded angles ; middle coxae similar in form, but larger ; hind 

 coxse very large, extending to the side margins of the body ; outer 

 surface flat; inner (or upper) surface with two obtuse prominences, 

 one near the front margin, the other about the middle, serving for 

 its firmer attachment. 



Legs short ; trochanters small, continuous with the outline of the 

 thighs and on their inner face ; thighs stout and compressed ; tibiae 

 compressed, triangular, rounded at tip, armed externally with long 

 spines ; terminal spurs long, slender ; front tibiae shorter and broader 

 than the others, being only one third longer than wide ; hind tibiae 

 more than two and a half times as long as wide, with two small 

 additional spines on the inner face, above the terminal spurs ; tarsi 

 five-jointed, a little longer than their respective tibiae, slender, some- 

 what compressed, spinous beneath, front and middle pairs with 

 joints 1-4 equal, iu the c? with one row of claviform membranous 

 appendages on each side, iu addition to the spines ; hind tarsi with 

 the first joint longer than the second ; articulations somewhat oblique 

 beneath, spinous, but without membranous papillse ; last joint of all 

 the tarsi one half longer than the fourth joint ; claws moderate in 

 size, simple. 



Body ovate elongate, depressed, resembling at first sight a minute 

 Blatta, a resemblance increased by the pale brown colour and some- 

 what translucent sides. 



The only representative of this family known is a small brown 

 insect 4 millims. long (Platypsylla castoris, Ritsema), found on the 

 American Beaver. Two specimens, collected from the Beavers in 

 the Zoological Gardens of Amsterdam, were most kindly sent to me 

 by Mr. Ritsema, who, on learning that my opinion of the relations 

 of the insect were quite different from those expressed by him, has, 

 in the most courteous manner, authorized and, indeed, requested 

 me to publish the results of my investigations as speedily as possible. 



Specimens were sent by the late Mr. Denny to Prof. Westwood, 

 who published a description of them about the same time, but a 

 little later than the notice by Mr. Ritsema, under the name Pla- 

 typsyllus castorinvs. I owe to the courtesy of Professor Westwood 

 an opportunity of making a hasty and somewhat superficial exami- 

 nation of his specimens during a visit in May 1871, when I stated 

 my belief that this insect would have to be regarded as Coleopterous. 



Proc. Zool. Soc— 1872, No. LI. 



