632 THE PANORPOID COMPLEX, ii., 



their bases are not preserved as well as those on the veins, and 

 very rarely show the two concentric circles which characterise 

 the base of a stiff and more upright bristle. In ray original de- 

 scription (5. PI. viii., fig. 6), I gave a diagrammatic figure of a 

 small portion of the archedictyon of this fossil, much enlarged. 

 I now consider this figure to be somewhat misleading, in that it 

 made the macrotrichia of the mesh%vork appear as large and as 

 clearly marked as those of the veins, whereas they are always 

 smaller, and in most parts of the wing more difficult to make out. 

 It will be readily seen from the photomicrographs that it is not 

 an easy matter to give a correct drawing of this meshwork, and 

 I think it better simply to give the photographs in this paper. 



So w^ell is this fossil preserved, that I have been able to find, 

 in several parts of the wing, by the use of careful lighting, 

 definite indications of the fine pitting due bo the presence of 

 microtrichia. Their bases of insertion are of about the same 

 diameter as that of the average particle in the grain of the rock, 

 viz., from 2 to 3/a. From a comparison with the microtrichia of 

 Panorpa, we may therefore conclude that the length of these 

 microtrichia was 40/x or more; i.e., considerably larger than an}^ 

 to be seen in existing Holometabola. 



Measurements of the beautifully preserved bases of insertion 

 of the macrotrichia upon the main veins of this fossil show that 

 the outer diameter of most of them lies between 30 and 40/x. 

 This is much in excess of the size to be found in the wings of 

 existing Orders, which seldom exceeds 10/x. Allowing some 

 expansion due to the pressure upon the wing during fossilisation, 

 it would still appear that this insect i30ssessed macrotrichia very 

 much stouter and longer than any now known to exist; their 

 probable length was between 300 and 400/^. The macrotrichia 

 upon the archedictyon were evidently smaller, and probably did 

 not exceed 200/x, their bases of insertion averaging only 20/v.. 



The cross-veins in the fossil are clearly seen to be developed as 

 strong struts between the main veins, and are quite independent 

 of the archedictyon. With the exception of <me or two macro- 

 trichia that appeal' to have strayed on to them from the latter, 



