306 THE GEOLOGICAL RECORD | < ' H . 



fused basally. The Protagrionidae (Protagrion audouini Brongniart) 

 had R and M separate, with a kind of arculus joining them some 

 way from the base. Such an arrangement places them as a side- 

 branch of the Order, which left no descendants even amongst 

 Mesozoic forms. 



An interesting fact in connection with Commentry is the 

 non-occurrence of larval forms. Without unduly stressing this 

 fact, we may couple it with the immense abundance of imaginal 

 forms which seem to have been suited to a life amongst damp 

 vegetation. Then we may well ask ourselves whether the larvae 

 of the Protodonata did not dwell in damp earth rather than in 

 water. The formation of the larval tracheal system (chap, ix) 

 undoubtedly proves that this was at one time the case. It may 

 well have been so in Carboniferous times. 



The insect-beds of Commentry occupy a comparatively small 

 portion of the total strata. They belong to the highest division 

 (Upper Zone) of the highest or Stephanian stage of the Upper 

 Carboniferous rocks of that region. Thus they really form a 

 passage-bed between the Carboniferous proper and the Permian. 

 The principal plant remains of this zone are the Giant Mare's-tail 

 (Catamites), characteristic of the coal-measures, and the large 

 Cycad Zamites, most abundant in Jurassic strata. Had the 

 insect-beds been isolated, instead of occurring at the top of a long 

 series of undoubted Carboniferous rocks, such a flora would have 

 placed them in the Permian. Emphasis is laid on this fact, 

 because the only known Permian Dragonflies are Meganeurids. 

 One of these, Ephemerites ruckerti Geinitz, is from the Lower 

 Permian of Germany, where a similar flora prevailed. The other, 

 Tupus permianus Sellards [if>0], is from the Permian of Kansas. 

 It is of interest in possessing a branched radius in all four wings, 

 with signs of a weak bridge and an oblique vein. 



We may picture to ourselves the giant insects of Commentry 

 as inhabiting the shores of a large, shallow, nearly stagnant lake. 

 In the muddy ooze around its borders grew forests of the Giant 

 Mare's-tail ; while, further back, on the sandy slopes, the graceful 

 Cycads and other extraordinary plants formed a more diversified 

 medley. There, amidst rotting vegetation, these insects lived and 

 bred. In such almost amphibious conditions, it may well be that 



