804 DR. LE CONTE ON PLATYPSYLLID.E. [Nov. 5, 



I must here return my sincere thanks to Messrs. J. Weyers and 

 Roelofs, of Brussels, for their kind aid in obtaining and forwarding 

 the specimens from Mr. Ritsema, and also to the Rev. A. Matthews 

 for his friendly offer to dissect one of the specimens for my investi- 

 gation — a task which he has accomplished with the same skill with 

 which he made his wonderful dissections of Trichopterygidce. 



It is very probable that a family showing such varied relationships 

 either was in former times, or is at present, widely diffused ; and it 

 is quite possible that, when looked for, similar Epizoa may be found 

 upon other aquatic mammals. The European Beaver, the Capy- 

 bara (Hydrochcerus), and the Musk-rat (Fiber zibethicus) should 

 particularly be examined for allied species. 



The generic characters are contained in the exposition of structure 

 given above, and, until other species are discovered, need not be 

 separated from those belonging to the family. 



Platypsylla castoris, Ritsema. 



Elongato-ovata, depressa, luteo-fulva, nitida, capite angulis 

 posticis pilis longis fimbriato, occipite spinis brevibus depressis 

 transversim uniseriatim pectinato ; prothorace trapezoideo, 

 antrorsum angustato, latitudine vix breviore, dorso parce 

 punctata, lateribus obliquis pro receptione antennarumsulcatis, 

 bast trisinuato, linea punctorum sinuata ante basin notato ; 

 coleopteris transversis, vage parce punctulatis, versus latera 

 pubescentibus, impressiorie brevi basali intra humeros notatis ; 

 abdomine segmentis dorsalibus serie transversa breviter setosis. 



Long. 4 millim. 



Platypsilla castoris, Ritsema, Petites nouvelles Entomologiques, 

 1869 (Sept. 15) ; Tijdschr. voor Entomologie, 2nd series, v. p. 185. 



Platypsyllus castorinvs, Westwood, Entomologist's Monthly 

 Magazine, vi. p. 118 (Oct. 1869). 



Collected by Mr. Riteema on the American Beavers (Castor 

 canadensis) in the Zoological Society's Gardens at Amsterdam. 



DESCRIPTION OF PLATE LXVIII. 



Fig. 1 . Upper surface of Platypsylla castoris. 



2. Under surface : a, presternum ; b, epistemum, and c, epimeron of pro- 

 thorax ; d, mesosternum ; e, cavity of middle coxa and side pieces of 

 mesothorax; /, metasternum ; g, cavity of bind coxa; h, bind coxa; i, 

 base of hind femur. 



The small front coxre are nearly concealed by the broad process of the 

 prosternum. 



3. Head, with antenna, dorsal view. 



4. Labrum, viewed from beneath. 



5. Antenna. 



6. Mandible, more highly magnified. 



7. Maxilla. 



8. Mentum, with ligula and labial palpi. 



9. Anterior leg. 



10. Anterior tarsus, more highly magnified, showing the series of membra- 

 nous papillse. 



11. Hind leg, with coxa. 



