290 Mr. R. I. Pocock on the Genus Theatops. 



rounded posterior angles, and a slightly concave posterior 

 margin. 



The dorsal plate of the anal segment quadrate, with straight 

 margins, raised lateral borders, and a conspicuous median 

 longitudinal sulcus. On each side the dorsal plate descends 

 so as to form the lateral portion of the segment and so as to 

 Ibe separated by but a narrow space from the ventral plate. 



The pleurae of the anal segment appearing in the narrow 

 space between the dorsal and ventral plates, extending behind 

 slightly beyond the margin of the ventral plate, but not 

 beyond the margin of the dorsal plate ; not armed with spines ; 

 thickly punctured. 



Tibige and tarsi of most of the legs armed below with a 

 strong spur ; claws of legs mostly armed. 



Anal legs very thick, punctured, without spines, in con- 

 tact ; the inner surface of the three proximal segments flat- 

 tened ; the upper inner margin of the proximal segment 

 raised. 



Claw of anal leg unarmed. 



Length about 20 millim. 



I have had no opportunity of examining the type specimen 

 either of Op. posfica, Wood, or of 0]). crassijjes, Meinert. 

 But the descriptions of these two species are so much alike 

 and are so applicable to Theatops postiea, Newport, that I 

 have without hesitation regarded the three specific names as 

 being referable to but one form. 



Dr. Meinert suggests that Op. spim'cauda, Wood, may be 

 synonymous with Th. posti'ca, Newport ; but if the figure 

 and description of the former species are to be trusted, the 

 two must still be considered distinct. 



EXPLANATION OF PLATE XVI. Figs. 6-10. 



Mff. 6, Anterior portion of the body of Theatops postiea (Say), seen from 



above. 

 Mff. 7. Head of ditto, seen from below. 

 Fiff. 8. Anal segment of ditto, seen from above. 

 Fiff. 9. The same, seen from below. 

 Fig. 10. The same, seen from the side. 



