AS COMPARED WITH THOSE OF LIVING TYPES. 187 



and to the Odonata in the strength and importance of the same ; and once more to the 

 Sialina in the form and manner of folding the wings ; while it has distinctive characters, 

 not only in the unusual combination of these peculiarities, but also in that the V. marrjinalis, 

 mediastina, and the main stem of the v. scapularis are equidistant and parallel throughout, 

 uniformly connected by straight cross-veins ; in the peculiar curving of the principal branch 

 of the v. scapularis ; in the mode of branching of the v. ezterno-media ; and in that the lower 

 principal fork of the v. interno-mcdia occupies more space witli its branches, and is of more 

 importance than the upper fork. 



The Palceopterina show their relation to the Termitina in the character of the v. mediastina 

 and the irregular cross-veins which run towards the margin ; to the Termitina more than 

 to any other, though not intimately in the mode of divarication of the branches of this 

 same vein ; to hardly any unless it be the Panorpina in the peculiarities of the v. extemo- 

 media ; to the Hemerobina and still more to the Sialina in the structure (though in Pate- 

 op terina given with more precision and exaggeration) of the v. interno-mcdia ; to the Eph- 

 emerina in the mode of branching, and to the Sialina in the important development, of 

 the v. analis ; to the Rhaphidiidae more than to any other, though but slightly, in the infre- 

 quency and manner of dispersion of the cross-veins, excepting the marginal ones ; and to 

 the Termitina in the obliquity of all the cross-veins apart from those on the margin, and 

 generally in the manner of folding the wings in repose. In the importance of the v. intcrno- 

 media and analis, occupying as they do fully half the wing, we have characters which of 

 themselves would clearly separate this family from the others ; we also find distinctions of 

 sufficient significance in every vein of the wing except the v. marginalis and mediastina. 



We have thus far treated only of the structure of the wings. In the Pataopterina, how- 

 ever, we have other portions of the body to examine in addition to these, though their 

 structure is generally scarcely as distinct as that of the wings, being crushed and displaced. 



The contour of the abdomen is best preserved, though least so at the terminal segment, 

 the most important part. It is apparently depressed ; the roundness of the lateral edges of 

 the segments indicate a membranous rather than a corneous, or even coriaceous integ- 

 ument, broad at the base, slightly increasing in breadth towards the middle and then taper- 

 ing considerably to the apex, the terminal segment apparently furnished with a pair of 

 short, stout, conical, anal stylets, — in all this corresponding in general to what we find in 

 some Sialina. The meso- and meta-thorax are somewhat indefinite in their outlines, but the 

 inequalities of the upper surface and the direction of the principal wing-nervures, which 

 afford lis an indication of the point of attachment of the wing, together with the faint sutu- 

 ral marks, show that it was similar in character in this part of the body also to the struct- 

 ure we find in Corydalis, one of the Sialina. The prothorax is quite remarkable for its 

 diminutive size, its width being only half that of the mesothorax. We find similar abrupt 

 changes in the Rhaphidiida3, but in the Pahcopterina the prothorax is not, as there, length- 

 ened anteriorly as a compensation, but is formed much as in Perlina, depressed, quadran- 

 gular, with a slight median carina, but its anterior edge produced in the middle to quite a 

 prominent tooth. The anterior legs are wanting, 1 but both the other pairs are present in 

 fragments, enough to show that they were of moderate length and strongly compressed, 



i It will be seen in our description of the anterior legs and reasons for this we have given elsewhere. See Amer. Journ. 

 of the head, that we interpret these parts very differently Science, (2) XL : 2GS. 

 froai Professor Dana in his article in Silliman's Journal. The 



MEMOIRS BOST. SOC. NAT. HIST. Vol. I. Pt. 2. 



