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the wing-sheath. Thus there is no difficulty in understanding how 

 a definite break or joint could be formed at the point where the 

 subcosta joins it. The joint would be formed merely by separation 

 of the block of chitin carrying the tooth beneath which the sub- 

 costa becomes united, from the next distally placed block. By 

 subsequent enlargement of these two depositions of chitin. the nodal 

 joint would be definitely formed. 



The form of the nodus in Mesophlebia does not, therefore, 

 preclude the supposition that this insect may actually lie in the 

 direct ancestral line of some of our recent dragon-flies. Unless the 

 basal half of the wing is discovered, and an examination made of the 

 region of the arculus and triangle, Mesophlebia must always remain 

 a puzzle. At present, it seems best to place it in a new sub-family 

 Mesophlebiinse. characterised by the form of the nodiis, the breadth 

 of the wing, and the closeness of the pterostigma to the nodus. As 

 stated before, this family may be only doubtfully added as a side- 

 branch to the sub-order Anisoptera. 



Order MECOPTERA (PANORPATJE). 



Family PANORPID^E. 

 Genus MESOCHORISTA, gen. nov. 



FOREWING. Outline oval ; cross-veins nearly all either absent 

 or so weakly developed as to be undecipherable in the fossil. Sub- 

 costa straight, parallel to costa, giving off a short slanting branch to 

 costa at about the middle of the wing-length. A small cross-vein 

 between costa and subcosta close to base. Radius curving away 

 from 8c near base, then straight and running nearly parallel below 

 Sc. Radial sector arising a little beyond one-fourth of the wing- 

 length, branching dichotomously ; each branch again dividing, the 

 upper one far distally, the lower close to its origin. Media arched 

 convexly costad near base, and soon branching into two ; the lower 

 branch is simple, continuing the line of the main stem straight on to 

 the middle of the posterior border ; the upper branch is divided 

 dichotomously, each division again branching into two, of which 

 the lower in each case again subdivides. First cubital vein weakly 

 developed, lying in a deep fold or concavity ; second cubital vein 

 strong, and straight, raised on a strong ridge or convexity. First 

 anal vein also convex and straight, nearly parallel to Cu2 ; second 

 anal vein weakly formed, lying in a concavity ; third anal vein short, 

 convex, and well formed. 

 C 



