Manchester Memoirs, Vol. Ixi. fiQi/), 'No. %. / 



lateral areas, whilst in the middle of the hinder border, the 

 convexity of the surface is carried out into a short, blunt, peg- 

 like prolongation, which just overhangs the prothorax. The 

 prothorax is short, low, and slightly ridged from side to side. 

 The mesothorax is large, its upper surface raised and slightly 

 convex, and bearing three low boss-like elevations, arranged 

 at the points of a triangle, the posterior one marking the apex 

 of the triangle, and being the most prominent. A small portion 

 of the flattened metathorax lies behind, in a triangular area not 

 covered by the wings. The forewings are folded in a posi- 

 tion of rest upon the body, and almost entirely overlap at their 

 free ends. 



The wings are \cry narrow at the point of attachment, and 

 broaden out rapidly to the wing apex. The length of the wings 

 is () mm., and their greatest breadth about 4 mm. 



The principal veins of the right wing are the more perfect, 

 those of the left wing, so far as they are discernible, being in 

 agreement. For pur^50ses of description we have therefore 

 selected the right wing. 



The wing structure of the insect is widely removed from 

 that of all known Palaeozoic forms, the nearest approach to a 

 similar wing structure that we know of being found amongst 

 the recent Scorpion-flies (/^rt«6'//zV/r<?), or the genxxsOrthophlebia, 

 established by Westwood and including several species found 

 in the Lower Lias of England, and the Upper Lias of Mecklen- 

 liurg. 



The Commentry insect has a simple structure, and less 

 branched principal veins than the Liassic forms, but is sub- 

 stantially the same. All the veins app)ear to spring from a 

 common root, and with the exception of the third vein, none are 

 sub-divided. The costal margin seems to have been extremely 

 delicate, and to have left very faint traces of its presence. In- 

 dications of It are present at the base of the wing, and upon 

 enlarged photograi)hs it is possible to distinguish fragmentary 

 portions along its whole length. 



The first vein, which one may regard as the sub-costal, 

 separates from the common root in the proximal third of the 

 wing, and passes straight out as an undivided vein to the wing 

 apex. It diverges very slightly from the outer margin along 

 Its course, and does not meet the latter until the well-rounded 

 end of the wing is reached. 



The next vein, which corres})onds to the radius, is the 

 most powerful of all. It follows a ]:)arallel course to the sub- 

 costal, giving off a radial sector at the end of the first third of 

 its length, and forks before reaching the margin. 



The radial sector diverges inwardly from the radius, and 

 divides up into three branches, which occu})y the inner portion 

 of the wing apex. 



Midway between the point of origin of the wing and the 

 division of the sub-costal and radius, arises a third vein, divid- 



