Sexual Dimorphism in the Rntelid genus Parastasia. 485 



P. niasiana, Ohaus, which is in my opinion the missing 

 counterpart of P. cphippium, v. Voll., to which it stands in 

 exactly the same relation as does P. Horsjieldi to the first, 

 except that the elytral mark is not absent but is of a 

 darker colour. la the type of P. niasiana this is of the 

 same shape as in P. ephippium except that its anterior 

 process does not quite reach the margin of the elytron ; 

 but, from the general terms in which Dr. Ohaus has referred 

 to it, it may not be alike in all specimens. The pygidium, 

 as in the preceding species, is less sharply striolated in the 

 male than in the female form and does not show a smooth 

 median ridge. In all other respects, except the greater 

 parallel-sidedness almost invariably characteristic of the 

 female and the slight interval between scutellum and 

 elytra to which Dr. Ohaus has called attention in P. 

 epthipinLtm, and which is evidently a female character, 

 the two are identical. The type of P. ejjhippimn was 

 brought from Sumatra, Dr. Ohaus's specimens are from 

 Nias, and two females in the British Museum are from 

 Penang. 



An interesting new species may be described here, 

 although only one sex is known, as it seems to form a link 

 between the present section of the genus and those dis- 

 tinguished, together with other characters, by a long 

 mesosternal process. It also exhibits in a more marked 

 degree the strange opaque area described in P. hinnana, 

 and distinctive of the female. 



Parastasia circumferens, sp. n. 



5 Crassa, nigra, nitidissima ; capite rugoso, acute quadridentato ; 

 prothorace lateribus disperse, antice fortius, punctato, utrinque 

 fortiter foveolato ; scutello elytrisque politissimis, his prope scutellum 

 sat late opacis ; pygidio cum propygidio subtilissime striolatis, illius 

 liuea media apiceque nitidis ; processu mesosternali valido acuto ; 

 tarsorum mediorum et posticorura unguibus divisis. Long. 21 m.m. 



Mas incognitus. 



If ah. Penang (Lamb). 



This insect presents a deceptive resemblance to P. 

 cp)hippium, which occurs in the same locality, and until I 

 had ascertained it by dissection to belong to the same sex 

 I believed them to be the two foi'ms of the same species. 

 In size, form and surface the new species exactly resembles 

 the old and it shows no structural distinction except in the 



