LITHOSIALIS. 45 



even nearer the base than its counterpart in the fore-wing, but its great length 

 is masked by the development of the median. Beyond the origin of the outer 

 branch the cubitus gives off three inward branches, the first forking. Owing to 

 the strong inward curvature of the cubitus and its branches, the succeeding anal 

 veins are directed almost straight inwards. The anal veins are six in number, the 

 first forking twice, and ending on the margin in three branches. 



The remaining veins are undivided. The cubital and anal veins of the 

 fore-wing are more obliquely disposed than those of the hind-wing, and the 

 latter has an anal area much larger than that of the fore-wing. 



The interstitial neuration consists of short stout cross-nervures, which 

 occasionally fork, and in the wider areas unite to form a meshwork. 



A triangular area is marked off from the base of each wing by a deep furrow. 

 This Woodward correlates with a similar area in the wing of Gryllacris (Cqrydalis) 

 brongniarti, which Swinton (' Geol. Mag., [2], vol. i, 1874, p. 337, pi. xiv, fig. 3) 

 has described as a stridulating organ. As stated elsewhere, I am of opinion 

 that Swinton's conclusions in the case of G. brongniarti were founded on a 

 misinterpretation of the wing, and that no stridulating organ, or similar 

 structure, is present. In the case of //. carbonarius such a structure would 

 apparently be useless, as none of the wings could come into such close apposition 

 as would allow-the structure to be used. I am unable to determine its purpose 

 or significance, unless it be a portion of the musculature attachment of the wing. 



Traces of a fore-leg are present, projecting from beneath the left' lobe of the 

 prothorax. Its structure is too indefinite for description. 



The wings were probably one-fourth or one-third longer than the portion 

 preserved — an estimate which would make each complete wing about 70 mm. long, 

 with a spread of about 140 mm., or inches. 



Genus LITHOSIALIS, Scudder. 



1881. Lithosialis, Scudder, Geol. Mag. [2], vol. viii, p. 299. 



Generic Characters. — Wings three to four times as long as wide. Outer and 

 inner margins almost parallel ; intercostal area wide basally, and diminishing to 

 extinction at apex of wing. Radius simple ; median with two main branches, 

 and cubitus large ; anal veins few and oblique. 



The wing on which this genus is founded is interesting as being the first 

 discovered in British Palaeozoic rocks, except the problematic examples mentioned 

 by Lhuyd and not otherwise known. Supposed to be a plant, the wing was 

 first sent by Mantell to Brongniart, who in turn referred* it to Audouin. The 

 latter recognised its insect character, and brought it before the Entomological 

 Society of France, the Academy of Sciences, and the Assembly of German 



