490 Charles Brongniart — Fossil Insects of the Primary Boclis. 



C. Scudderi (Plate XIT. Fig. 3), C. gracilis, created for some insects 

 of the smallest size, but whose body measures 4 to 5 centimetres in 

 length ; the spread of the fully-extended wings is about one deci- 

 metre ; the body is more blunt than that of the Woodwardia, it is 

 also less cylindrical. The neuration is analogous to that of the 

 preceding genus ; the nervures and nervules are nevertheless more 

 abundant, and the wings are not coloured. 



But this genus presents a very curious peculiarity upon whicli it 

 is well to insist. Firstly, I would remind you that insects breathe 

 b}^ the aid of tracheae, whose distribution in the body is vainable. 

 Among perfect insects these tracheas open externally by orifices 

 which are called stigmata; these generally breathe the ordinary 

 atmospheric air. 



A great number of larvee, especially those of the Neuroptera and 

 of the Orthoptera, are aquatic, and the organs of respiration are 

 modified. The tracheee, in place of ending suddenly and presenting 

 openings or stigmata, ramify endlessly. Sometimes the extremities 

 of the trachete are free, at other times they are united in some kind 

 of foliaceous organs. The insect then breathes the air contained in 

 a state of mechanical solution in the water, either by the aid of 

 branchial tufts, or by the means of branchial plates. 



Among the larvae of the Ephemera the first seven rings of the 

 abdomen show on each side a foliaceous organ, in which the trachege 

 are seen to ramify. The oscillations of these appendages maintain a 

 continuous current around the larvae; these organs are only lost at 

 the time of passage to the state of the sub-imago. 



In 1848 Newport made known a pseudo-Neuropterous insect of 

 the family Perlidee, the Pteronarcys regalis, which presents in the 

 adult state, on the under part of the abdominal rings, some branchial 

 tufts protected by a sort of pocket, and besides which it is provided 

 with stigmata. This insect is amphibious, it can breathe the ordinary 

 atmospheric air and the air which is contained in mechanical solution 

 in the water. 



The CorydaJoides (mihi) offers in the adult state an analogous 

 disposition of the organs of respiration. Each one of the abdominal 

 rings presents a plate on each side, where one can distinctly see, 

 even with the naked eye, the branching out of the trachcEe. I have, 

 besides, been able to verify the presence of stigmata. I possess ten 

 impressions of this genus. 



It is then permissible to suppose that these insects were amphibious 

 like the Pteronarcys. Like the latter, it presents at the extremity of 

 the abdomen two multi-articulate filaments. 



I shall place by the side of these Megasecopterida an ancestral 

 type of the Libellulse ; for which the creation of the family Proto- 

 donata and the genus Protagrion seems to me necessary. At present 

 only a single wing has been found at Commentry. It measures 10 

 centimetres in length and two in breadth. Its form, its neuration, 

 and its reticulations remind one much of the living Odonata. There 

 are, nevertheless, some rather notable differences. 



The third family, that of the Horaothetida of Scudder, contains 

 some insects of more modest size, slenderer bodies, more sessile 



