486 Charles Brongniart — Foml Insects of the Primary Rochs. 



ptera ; they are generally considered as being a primordial type of 

 insects. No author has described them as occurring in the system 

 with which we are now engaged. Nevertheless they existed as 

 early as the Carboniferous period, for 45 specimens have been found 

 at Commentry. 



It is difficult to see the number of the joints of the legs, of the 

 palpi and of the antennse ; but these organs can be discerned upon 

 several specimens. 



The body is cylindrical, becoming thinner at the posterior part, 

 and terminated by a multi-articulate filament as long as the body. 



The antennee and the legs are thick and short, the head is rather 

 large. The prothorax is very narrow, the mesothorax and the 

 metathorax are co-equal and much longer than the prothorax. 



The segments of the abdomen are ten in number and equal in size, 

 the last only being a little longer than the rest. 



It appears to me that upon one of the specimens some abdominal 

 plates are seen, as has been observed on Machilis. 



The whole of the body (antennge, legs, thorax, abdomen) is 

 covered with very numerous and very short hairs. The body with 

 the abdominal filament varies in length between 15 and 22 millimetres. 



This insect resembles Lepisma and Machilis. It differs from them 

 in several characters, but the principal difference consists in the 

 presence of a single abdominal filament in the fossil species. I shall 

 designate this ancestor of the living Thysanura by the name of 

 Dasyleptiis Lucasi, dedicating it to M. H. Lucas, of the Paris Museum. 



Among the Orthoptera a great number of Blattse or of Palseo- 

 blattariee (Scudder) have been described, and Mr. Scudder has classed 

 them in several groups. As he has made a special study of them, it 

 is not necessary to speak of them here. 



Goldenberg has named a wing Fulgorina Klieveri, which must have 

 belonged to a large Blatta; we shall designate it by the name of 

 Megahlattina Klieveri. 



Another family of Orthoptera was pretty well represented, which 



I propose to call Palgeacridiodea. The first group contains many 

 genera ; the (Ediscliia (mihi), of which the third pair of legs re- 

 semble those of living locusts. The Sthenaropoda (mihi), near allies of 

 (Ediscliia, but whose legs are thicker and shorter, and less fitted for 

 leaping. 



The genus Frotogryllacris (mihi), represented by an insect called 

 Corydalis, then Gryllacris, and afterwards Lithosialis, ought to be 

 changed in order to show that this insect did not resemble Sialis. 



A fourth genus, Paolia (Scudder), including many species, should 

 be included in this first group. 



The second group contains three genera, namely : — 



Sihenarocera (mihi), insects with strong and long antennae, short 

 body, and thick, long legs, and long and narrow wings, recalling 

 somewhat those of the Pachytylus. These insects measure fully 



II centimetres from the anterior part of the head to the extremity 

 of the wings, wlien the latter are folded upon the back. 



Caloneura (mihi) is nearly related to the foregoing ; but the legs 



