feY R. J. tillyard. 189 



This new Order is proposed for the reception of a very 

 remarkable fossil from the Ipswich beds, represented by fore- 

 and hindwings, very beautifully preserved The insect forms 

 the direct connecting link between the Palaeozoic PaUeodicty- 

 optera on the one hand, and the recent Mecoptera on the other. 

 Tlie Pala;odictyopterous character is seen in the primitive, almost 

 Blattoid, scheme of venation (which is, of course, preserved also 

 better in Mecoptera than in any other recent Order, but with 

 great reduction), and the presence, in its last stage of evolution, 

 of the dense reticular mesh work of polygonal cellules so charac- 

 teristic of this ancient Order. In the Protomecoptera, as exem- 

 plitied by this Ipswich fossil, the development of hairs upon both 

 veins and membrane is very pronounced: and the wings exhibit, 

 in a remarkable manner, the method by which hairs first ap- 

 peared upon the wing-membrane; just as Mesogereo7i, another 

 Ipswich fossil, exhibits the first formation of tubercles in the 

 Hemipteroid wing. Another exceedingly archaic character, 

 long since lost in most insect-wings, is the presence of a true 

 costal vein, not fused w4th the costal border of the wing. 



The Mecopterous characters are very obvious, for the wings 

 are clearly built upon the Panoipid venational plan. The 

 essentials of this are — 



(1) Close similarity between fore- and hind wings, with onlv 

 slight differences in venation. 



(2) Symmetrical dichotomous branchings (bilateral forks) of 

 Rs and M, as opposed to tlie unilateral or unsymmetrical fork- 

 ings of these same veins seen in the Odonata, Neuroptera, etc. 



(3) Transverse veins few, and so arranged as to support the 

 bilateral forks. Thus are formed the typically Panorpoid 

 elongated polygonal cells of large size, and varying fiom five to 

 seven sides. The true Mecoptera have, typically, twelve of these 

 cells lying completely within the wing between Rs anteriorly 

 and M-M4 posteriorly, but the number may be i-educed by sup- 

 pression of cross-veins. In some fossil Mecoptera, the number 

 may be greater. In the Protomecoptera. there are twe/nty of 

 these same cells. 



In view of the fact that some of the present-day ^Mecoptera, 



