426 SCIENCE PROGRESS 



forms, e.g. Lithomantis carbonariiis (fig. i6), Stenodictya lobata^ 

 Homaloneurina Bojinieri, Honioioptcra IVoodzvardt, Honioeophlcbia 

 gigantea ; gill-like pleurae occur in each abdominal segment 

 in Stenodictya lobata ; and Corydaloidcs Scudderi possessed 

 tracheal gills (containing distinct tracheae) in the imago, similar 

 to the tracheal gills of certain Ephemerid larvae of the present 

 day. In the imago of the living Perlid Pteronarcys tracheal 

 gill-tufts actually persist (fig. 17). It is also of interest to note 

 that the larvae of PerUdce have rather large compound eyes, 

 the ocelli being merely opaque spaces. The future wings 

 are represented in these larvae by lobe-like prolongations 

 (varying in length according to age) of the meso- and meta- 

 notum. Many of the Pcrlidce also present the curious pheno- 

 menon of micropterism amony the males, e.g. Taeniopteryx, 

 Ncmoura trifasciata^ Pcrla maxima^ Dictyopteryx microcephala^ 

 Isogenus nubecula. It is not impossible that these cases may 

 be instances of reversion in a primitive group of insects (all 

 with feeble powers of flight), which has progressed only slightly 

 in comparison with the majority of insects from the ancestral 

 Carboniferous stock. 



In the Protephemerid division of the Palaeodictyoptera the 

 wings could not be folded back over the abdomen, but remained 

 horizontal when at rest and were only capable of motion in one 

 plane, a characteristic which has been retained by the modern 

 Ephemera. Some Carboniferous larval forms clearly show a 

 gradual development of the wings, standing out horizontally at 

 right angles to the body. 



Representatives of the heterogeneous group of Myriapods ^ 

 occur at an earlier date than insects, for the Archidesniidcc {^2iva- 

 pecaris and Archidesmus) have been found in the Old Red 

 Sandstone of Scotland.^ These forms, together with the 

 numerous Carboniferous Euphoberiidce (fig. 18) and Archijididce 

 are placed in a special order, the Archipolypoda, differing from 

 the DiPLOPODA in the dorsal scutes being more or less divided 

 into two parts instead of being fused into one but agreeing 

 with them in there being two pairs of legs to each ring, 



' The Chilopoda, Symphyla and Diplopoda are now usually treated as 

 independent classes. 



* Peach, B.N., Proc. Roy. Phys. Sac. Edin. vii. (1882), p. -]•] ; xiv. (1899), 

 p. 113. 



