1872] DR. LE CONTE ON PLATYPSYLL1D.E. 803 



The antennae are only slightly modified from the irregular form 

 seen in the Gyrinidcs and certain genera (Parmis, Helichus, Sec.) of 

 Pamidce ; the reception of the antennae in cavities on the dorsal 

 surface of the prothorax is a rare character, but occurs in Physemus, 

 Lee, of the Byrrhidcs, Mychocerus, Er., of doubtful position, and again 

 in a totally different genus, Usechus, Motsch., of the Tenebrionidcs. 

 In all the genera mentioned the club of the antennae is globose, and 

 the cavities are round fossae, near the front angles of the pronotum ; 

 their extension into grooves, longer than the antennae themselves, as 

 in Platypsylla, is the first instance known, and certainly one of the 

 most remarkable characters of the genus. 



The prothorax is not unusual in form, being somewhat like that 

 of Silpha, with the addition only of the singular antennal grooves 

 just mentioned ; the transverse rows of punctures near the basal 

 margin recall those seen in Dytiscidce and Gyrinidcs. 



The immense development of pro- and mesosternum is very 

 similar to that of Limulodes, a very abnormal North-American genus 

 of TrychopterygidcB ; but, in addition, the metasternum is similarly 

 and equally developed, a character peculiar to this family. 



The coxae are somewhat peculiar, feebly resembling those of 

 Gyrinidcs ; but the side pieces of meso- and metathorax are quite 

 different from those of that type, and are strongly Trichopterygidan 

 in their form. The hind coxae of Gyrinidcs, moreover, are contiguous 

 for a long distance on the inner margin (as is also the case in Dytis- 

 cidce and Amphizoidcs) ; and the coxal articulation is quite different. 



The elytra are similar to those of Omalium and many other 

 Staphylinidcs, but are peculiar from the absence of distinct epipleurae, 

 a rare character in the first primary division of Coleoptera ; the 

 suture is slightly imbricated, though less so than in Xantholinus 

 and allied genera of Staphylinidcs. 



The abdomen presents nothing particularly worthy of mention, 

 being similar to that of many Staphylinidcs ; the concealment of the 

 first ventral segments by the hind coxae is remarkable. An ap- 

 proach to this arrangement may perhaps be observed in the so- 

 called ventral plates of Cyllidium of the Hydrophilidcs. 



The only peculiarity worthy of notice in the legs is that the front 

 and middle tarsi of the J are furnished with two rows of papillae, or 

 clavate, flat, membranous appendages, similar to those seen in 

 various groups of the adephagous series. Otherwise the legs are not 

 very dissimilar to those of some genera of Anisotomini (Cyrtusa, 

 Co/enis, &c), a tribe of Silphidce. 



It will be seen by the above analysis of characters that the affini- 

 ties of this insect are very composite, but all in the direction of the 

 Adephagous and Clavicorn series, though chiefly with the latter. 

 The most convenient position of the family will probably be between 

 Hydrophilidcs and Leptinidcs as the families are now arranged, 

 though its tendency to Trichopteryyidcs and Corylophidcs is equally 

 strongly manifested. 



It is therefore a very peculiar and extraordinary synthetic type, 

 which is almost equally in and out of place in any linear arrange- 

 ment of the series with which it is allied. 



