AIR-BREATHERS OF THE COAL PERIOD. 281 



J'ig. 51. — Pupa Vetusla, apex magnified. 

 u 52. — " " sculpture of surface magnified. 



" 53. — " " cellular structure of shell highly magnified. 



" 56. — Eye of an Insect, natural size and magnified, and three ocelli 



highly magnified. 

 " 57. — Xylobius Sigillaria, Anterior segments magnified. 

 " 58. — " " natural size. 



" 59.— " " part of one of the posterior segments 



magnified. 

 " 60. — " " caudal extremity magnified. 



" 61.— " head magnified, showing the eyes. 



XIII. — Characters of the Animals described in this paper. 



To facilitate comparisons, I propose in this section to give an 

 abstract of the leading structural points which may serve to dis- 

 tinguish the animals described in this paper from each other, and 

 from such new species as may be discovered either in Nova Scotia 

 or elsewhere. The characters given must necessarily be incom- 

 plete, and I shall confine myself to points distinctly ascertained 

 and likely to be met with in any additional specimens which 

 may be discovered. 



Province.— VERTEBR ATA . 

 Class. — Reptilia. 

 Order. — Microsauria. 



Genus. — Hvlonomus. 



Reptiles or batrachians ; with simple teeth in one series ; bi- 

 concave vertebrae with arches anchylosed to them ; ribs long and 

 bent ; limbs developed for walking ; cranial bones smooth or 

 nearly so ; body protected below with oval or ovate bony scales, 

 and above with horny scales and other appendages. 



1. Hylononius Lyelli^ Dawson. — Teeth elongated, conical, 

 thirty-six in each side of the jaw; larger toward the anterior 

 part of the lower jaw ; length of lower jaw .7 inch ; limbs well 

 developed, especially the posterior pair ; bony scales oval ; body 

 above with imbricated horny scales, and rows of angular and 

 bristly points. 



2. Hylononius aciedentatus, Dawson. — Teeth of maxillary and 

 mandible thick wedge form, or nearly round at base and flattened 

 to an edge at top. Teeth of intermaxillaries cylindric, bluntly 



