590 IV AR TRâGÂRDH 



they are very narrow, and of even width for a short distance, 

 whereupon they widen shghtly, and end with sharply ponited 



tops. 



Maxillary plates short, not attaimng one third the length 



of the lobes. 



Maxillary palpi short, without any peculiar features except 

 that the ventral edge of joint I is a thin blade with dentate 

 edge. 



Ventral side. 



Tristosternumof very exceptional shape (fig. 113), nowhere 

 else met with in the Parasitidae. 



The trunk is, as is usiial in the Uropodinae, large and wide, 

 conical, twice as wide at the base as it is long ; feathered shp 

 single, five times as long as the trunk, and with only 3 to 

 4 branches. 



The most remarkable feature is, however, that a pair of 

 very thin, triangular, free blades are fused with the trunk 

 along the basai half of its sides ; they are finely pointed, Avith 

 straight exterior sides, while the médian ones bend at a right 

 angle towards the tritosternum, on a le vel with the middle 



of it. 



It is difïicult to interpret thèse structures. It seems, however, 

 unlikely that they were originally parts of the tritosternum 

 because, whether the trunk is narrow, cyHndrical, or conical, 

 or rectangular, it is always single, with one exception, Uro- 

 dinychus Krameri (G. Can), in which it has a pair of small teeth 

 ventrally. The blades in U. acuminatus are placed in exactly 

 the same position as the jugular shields, where such are 

 présent ; and it seems most plausible that they are highly 

 modified jugular shields. In the true Uropodinae the latter 

 hâve to ail appearances undergone a far more pronounced 

 change in structure and position (compare Tragardh 1908, 



p. 40 and 44). 



Sternalshieldfusedwiththeendopodal shields (fig. 113), 



but still very clearly defined on account of its différent struc- 



