448 SAMUEL H. SCUDDER ON 



not quite clear nor consistent), while in no other species is the fan-like disposition of the 

 rays of the externo- and internomedian veins so well shown as here; they divide the field 

 very equally between them, the externomedian vein forking far back toward the base; and 

 the large anal area with its almost regularly arcuate anal furrow and parallel veins oc- 

 cupies about a third of the inner margin. The nervules on the two sides of the wing 

 are of similar distance apart and rather crowded. I have not seen specimens of this 

 species but describe it briefly from the figures. 



The length of the wing is 15.5 mm; its breadth 5.5 mm; it comes from the Lias of 

 Schaiubelen in Switzerland, and is known from a single wing. 



Rithma Morrisi. 



[Without name] YVestw., Quart. Journ. Geol. Soc. Loud., x, 390, PI. 18, fig. 31. 

 Rithma 3Iorrisi Gieb.. Ins. Yorw. 319; Scudd., Proc. Acad. Nat. Sc. Philad., 1885, 



113, 114. 

 Blattidium Morrisi Heer, Yiertelj. naturf. Gesellsch. Zurich, ix, 290. 



A single nearly perfect wing, known to me only by Westwood's figure, is closely relat- 

 ed to R. formosa, but is smaller, has its greatest width close to the base, has even more 

 crowded veins, with more abundant dichotomizing and a much smaller not protruding 

 anal area. The humeral field is very small but not slender, the costal area as in R. for- 

 mosa, but terminating just above and not embracing the tip, the median veins much as 

 there but with more abundant forking of the branches. The anal furrow appears to be 

 bent roundly in the middle and to be oblique apically, yet not to reach even a fourth way 

 down the inner margin. 



The length of the wing is 10 mm. and its breadth nearly 4 mm. The specimen "comes 

 from the Lower Purbecks of Durdlestone Bay, England. 



Rithma purbeccensis. 



[Without name] Yfestw., Quart. Journ. Geol. Soc. Lond., x, 390, PI. 18, fig. 32. 



L'illima purbeccensis Gieb., Ins. Yorw., 319; Scudd., Proc. Acad. Nat. Sc. Philad., 1885, 



113, 114. 

 Blattidium 2>urbeccensis Heer, Yiertelj. naturf. Gesellsch. Zurich, ix, 290. 



This wing is only known to me as the last, and it is less perfect, but has characteris- 

 tics which easily distinguish it. It is probably broadest in the middle of the basal half 

 and has the typical wedge shape. The humeral field is large and broad, tapering much 

 apically and reaching more than one-third way down the costal margin. The mediasti- 

 no-scapular vein is very sinuous, making the costal area broadest in the middle of the 

 apical half of the wing where it occxipies two-thirds of the entire breadth, but as the 

 vein curves upward again apically and probably strikes the exact tip of the wing, it nar- 

 rows rapidly at the end; the area is filled with crowded, sinuous or arcuate, partially 

 forked nervules, which are much more crowded than the distant, slightly forked, sinuous 

 branches of the externomedian and internomedian veins, which appear to divide the space 

 to the anal furrow about equally between them. The anal furrow is strongly arcuate in 



