MESOZOIC COCKROACHES. 449 



the middle and terminates as far out as the humeral field and far beyond the basal branch- 

 ing of the externomedian vein; anal veins not preserved. 



The length of the fragment is 10.5 mm. and the presumed length of the wing 11.3 

 mm.; its breadth is 3.5 mm. It comes from the Lower Purbecks of Durdlestone Bay, 

 England. 



Rithma Daltoni sp. nov. 



PI. 46, fig. 16. 



The single wing sent to me by Mr. Brodie is preserved in a similar manner as It. jxtr- 

 beccensis and was at first taken to be the type of that species, but a closer examination 

 showed that if the latter has been correctly drawn by Westwood, this must be distinct 

 from it. The wing is of the same color as the dirty chalky white stone on which it rests, 

 the veins even showing no color distinction. These are finely impressed, showing as 

 well as the slightly arched surface that its upper side is seen ; there are some faint inter- 

 calary veins in the costal area not shown in the figure; the anal furrow is no more deeply 

 incised than are the others, and the humeral field is flat and at a lower level than the rest. 

 The wing is undoubtjdly broadest in the middle of the basal half, is wedge-shaped, ta- 

 pering very regularly and considerably, with a straight inner and gently convex costal 

 margin, to a somewhat pointed (here broken) tip. The humeral field, at first equal, 

 tapers in the apical half, which reaches nearly to the middle of the wing. The medias- 

 tino-scapular vein is broadly sinuous, giving the costal area the same shape that it has 

 in JR. jnirbeccensis, including the entire tip of the wing, the extremity of the vein passing 

 a short distance below the very apex; its branches are nearly straight, parallel and 

 oblique, the early ones simple, the later, arising in the broadening field, forked, the forks 

 originating on a line with the bases of the simple veins. The remainder of the wing is 

 as in It. purbeccensis, only the branches are equally distant on the two sides of the wing. 



Length of the fragment 10.75 mm.; probable length of wing 12 mm.; its breadth prob- 

 ably 4 mm., though the extreme breadth at the tip of the anal furrow is slightly less, 

 or 3.85 mm. The specimen comes from the English Purbecks, and the species is named 

 for Mr. W. H. Dalton of the Geological Survey of Great Britain. 



Rithma Westwoodi. 



PI. 46, fig. 11. 



[Without name] Westw., Quart. Journ. Geol. Soc. Lond., x, 390, 396, PI. 18, fig. 22. 



Rithma Westwoodi Gieb., Ins. Vorw., 318-319. 



Blattidium Westwoodi Heer, Viertelj. naturf. Gesellsch. Zurich, ix, 290. 



Among the specimens sent me by Rev. P. B. Brodie, one occurs which seems to be the 

 type of Westwood's figure, since in all that I have seen the figure is reversed, and in this 

 instance the resemblance is close. I am able, therefore, to describe this species from the 

 original and find the doubts I expressed concerning its position (Proc. Acad. Nat. Sc. 

 Phdlad., 1885, 113) hardly to be confirmed, though of all the species of Rithma it is the 

 most closely related to Mesoblattina. 



The under surface is exposed, the specimen being transversely concave, with elevated 

 veins and concave interspaces: all are of the same color as the dirty chalky-white stone. 



