INSECT A. 185 



these is uncertain, and they seem to have possessed the 

 anomalous character of a row of dorsal spines. In the Litho- 

 graphic Slates of Solenhofen (Middle Oolites) occur the 

 remains of an animal which is referred to the Myriapoda by 

 Count Miinster, under the name of Geophilus proavus. Other 

 Myriapods have been described from Tertiary strata and from 

 amber. 



CLASS INSECTA. 



The Insects are Articulate Animals, in which the head, thorax, 

 and abdomen are distinct from one another. The thorax consists 

 of three segments, each of which carries a pair of legs. Mostly 

 there are two pairs of wings borne by the two hinder segments of 

 the thorax. The abdomen never carries locomotive limbs, but the 

 last abdominal segments may carry reproductive or sensory appen- 

 dages. A single pair of jointed antenna is present, and the eyes are 

 generally compound. Respiration is effected by air-tubes (trachetR). 



As regards the general distribution of the Insecta in time, 

 the oldest-known forms are from the Devonian Rocks of North 

 America. Here occur the remains of several insects which 

 belong to the order of the Neuropterous Insects (or to the 

 Pseudo-neuroptera). Amongst the most remarkable of these is 

 the Platephemera antiqua of Mr Scudder (fig. 128). This 

 species must have attained a 

 large size five inches in ex- 

 panse of wing and it is re- 

 garded by Mr Scudder as 

 being referable to the Ephe- 

 merida (the May-flies). This 

 eminent authority, however, 

 regards it as a "synthetic 

 type ; " that is to say, as a 

 form combining peculiarities ~ 



. r jr lg . I2 8. Wing of Platephemera antiqua 



Of Structure which are nOW (after Dawson), Devonian, 



only found indifferentgroups. 



Three other genera belonging to the Neuroptera have been 

 described from the Devonian Rocks of North America, under 

 the names Homothetus, Lithentomum, and Xenoneura. 



In the Carboniferous Rocks, the remains of Insects, as might 

 have been expected, are comparatively more abundant, though 

 still far from common. In the rocks of this period we have 

 representatives of the orders Neuroptera, Orthoptera, and Coleop- 

 tera (Beetles). The Neuroptera are represented by a remark- 

 able form, which has been referred to the Ephemerida under 

 the name of Haplophlebium Barnesii (fig. 129). This insect 



