264 Dr. Malcolm Burr on the Opisthomeres 



Verhoefi calls the big plate the pygidium, the small one 

 the siipra-anal plate, which is the same as the telson ; 

 Zacher also calls it the supra-anal plate, adding that no 

 trace of the metapygidium remains, by which he implies, 

 I suppose, that the latter has been entirely absorbed in 

 the telson. 



Perhaps we are both wrong, as the interpretation may 

 be that the pygidium is very big, the metapygidium very 

 small, and the telson disappeared; or that the meta- 

 pygidium is fused into the pygidium, 



I have unfortunately no Labiine opisthomere available 

 at the moment, but those of the Chelisochid Adiathetus 

 tenebrator are very remarkable. The basal plate is a little 

 longer than broad and shows a reinforcement which may 



Fig. \3.— Adiathetus tenebrator, Kirby, 6 ■ 



represent the absorbed metapygidium. The apical seg- 

 ment, which may be the metapygidium, or the telson, or 

 both, is complex : there is an irregularly shaped, chitinous 

 plate, with a deep incision in the posterior margin, which 

 throws ofi laterally long acute lobes which are but feebly 

 chitinised, apparently the homologues, the rounded or 

 strengthened lobes of the Psalis or AUistethid opistho- 

 meres : beyond this is a faint membrane, with, a few 

 bristles, which I read as the telson. If this is so, we have 

 here a more generalised form of opisthomeres than in the 

 Bracliylahidae and in Labidura. 



Of the Anechurinae I have examined two species, Meso- 

 chelidura bolivari, and Anechura bipundata : in both, there 

 is no trace of any third plate. The basal one is broad 

 at the base, gradually narrowed towards the truncate 

 apex. The apical plate is folded backwards at this 



