MESOZOIC COCKROACHES. 445 



the costal area distinguishing it from the former, the greater obliquity of the inferior 

 nervules and particular!}' those of the internomedian area, as well as the parallel and 

 similar course of the anal nervules, separating it from the latter. 



Most of the species come from the English Purbecks, but two occur in the Lias of 

 England and Switzerland. 



Rithma Stricklandi. 



PL 46, figs. 4, 5. 



Blatta Stricklandi Brodie, Foss. Ins. Engl., 32, 118, PL I, fig. 11 (2 figs.) ; Gieb., Ins. 



Vorw., 317. 

 Blattidium Stricklandi Heer, Viertelj. naturf. Gesellsch. Zurich, IX, 290. 



By the favor of Mr. Brodie, I have had the opportunity of studying and redrawing 

 the original of this species, which shows a complicated cross-neuration by the overlap- 

 ping of the four wings and the tenuity of the membrane. This lias enabled me to trace 

 out the separate neuration of the tegmina, as shown in fig. 1. which would not have 

 been possible from the original drawing, which was in other respects not wholly correct. 

 No description accompanied the figure. 



The most perfect wing is the upper wing of the left side, and this is onlv preserved 

 sufficiently to show that it probably belongs in this genus and cannot be identified with 

 any other of the species here referred to Rithma. The humeral area is very narrow, and 

 is not differentiated from the rest by its flatness; the costal area of nearly equal breadth 

 until close to the tip as in the next species, but the main vein has a slight sinuosity and 

 no terminal inferior forked vein, and its branches are comparatively few and distant. So 

 too, are the branches of the externomedian, which in other respects do not differ from the 

 next species. In the hind wing, the costal area is much narrower and distinctly tapers 

 apically. The inner bases of all the wings are wholly obscured by the meso- and meta- 

 thoracic scuta, which come to the surface as large spots, so that there is no indication 

 even of the anal furrow; they indicate, however, the position of the bases of the win--, 

 enabling us better to judge of their exact length, while the curves show where the tip 

 must lie. Judging by these, the length of the wings was 12 mm.; the breadth of the 

 two wings at rest 5.5 mm.; that of one of them, probably about 4 mm.; and the width of 

 the mesothorax, 3 mm. 



The specimen comes from the Purbecks of the Yale of Wardour, Wiltshire, England, 

 and is of the same color as the dirty brown stone on which it rests, excepting that parts 

 of the thorax are black, the veins varying from light to blackish brown. The surface of 

 the specimen is very slightly convex, and the veins are slightly impressed. 



Rithma Gossii sp. nov. 



PI. 46, fig. 15. 



This species is founded on a nearly perfect wing in which only the anal area is miss- 

 ing. The wing is of nearly uniform width, nearly three times as long as broad, witli a 

 well rounded tip. It is of the same color, veins and all, as the dirty, chalky-white matrix; 



