ORTHOCOSTA SPLENDENS. 27 



shows that its origin is of much older date. The cubito-median Y-vein lies close 

 to the outer median for a short distance, and then bends obliquely inwards to the 

 margin of the wing. The inner cubital vein is fairly straight, and widely spaced 

 along almost its whole length from the cubito-median Y-vein. 



Six anal veins are present, all going obliquely to the inner margin, the second 

 and third alone forking. The interstitial neuration, which I have been able to 

 study better by immersing the specimen in water, consists of numerous irregular 

 cross-nervures, occasionally uniting in crossing, or forming a loose meshwork, 

 especially between the median and cubital veins. 



Affinities. With so small a wing- fragment, and with few wings of similar 

 character as guides, it is not possible to form an accurate idea of the whole wing. 

 The radius and radial sector entered the wing-apex, and the median-cubital 

 elements occupied the greater part of the inner margin of the wing. 



The broad intercostal space and the course of the subcosta are very similar to 

 those in Polycreagra elegants, Handlirsch, but the general trend of the main veins, 

 and most of all the character of the interstitial neuration, are so suggestive of 

 Dicti/oneura libeUuloide*, Goldenberg, that I had referred the specimen to that 

 genus before Handlirsch's paper was published. 



Handlirsch has now (1919) referred this species to a new genus, Sherboniiella, 

 giving the new name " for the sake of uniformity," but without diagnosis. 



Family ORTHOCOSTID^E, Bolton. 



1912. Boltou, Quart. Journ. Greol. Soc., vol. Ixviii, p. 313. 



Wings with almost straight outer margin; inner margin well rounded; costa, 

 subcosta and radius closely approximated ; median, cubitus and anal veins 

 occupying nearly the whole of the inner half of the wing. 



Genus ORTHOCOSTA, Bolton. 

 1912. Orthocosta, Bolton, toe. cit., p. 313. 



Generic Characters. Radial sector diverging from radius, and with few 

 divisions. Median with two branches united by a commissure. Cubitus stout, 

 forked near base, the outer branch forking twice, and the inner once. Anal area 

 elliptical. Interstitial neuration forming an open polygonal meshwork. 



Orthocosta splendens, Bolton. Plate I, fig. 2 ; Text-figure 1. 



1912. Orthocosta splendens, Bolton, Quart. Journ. Geol. Soc., vol. Ixviii, p. 310, pi. xxxi, figs. 13. 



Type. Incomplete wing, and impression; Moysey Collection, Museum of 

 Practical Geology, Jermyn Street (nos. 30,222 and 30,223). 



