PAL.EOZOIC AIR-BREATHING ANIMALS. 73 



class Amphibia ; but some of them approach in certain important characters, as in the deve- 

 lopment of the ribs and chest, and therefore of the respiratory and circulatory power, to the 

 true reptiles. In the Permian, the newest system of the Paheozoii-, true reptiles have been 

 found in Europe and in the United States; Init not as yet 'u\ Canada, tlmngh tu()tj)rints of 

 reptiles or amphibia occur in the upper member of the Carboniferous. 



The Canadian species have all been grouped for the present in the order Stecjocephala. 

 In general form, those hitherto found in Canada are lizard-like, with four limbs, often 

 well developed, and usually with five toes. The arrangement and division of the cranial 

 bones resemble those in modern batrachians. The ribs are usnally Iniiu- and curved. The 

 vertebrfe are often only imperfectly ossified, but their processes arc well developed. The 

 body is protected below by bony plates and overlapping bony scales, and in some species the 

 back has spines, tubercles and horny scales. The order has been divided into suli-orders, 

 based on the more or less perfect ossification of the vertebrre, viz., (1) LcptosjuDhJuli, or those 

 having the vertebras merely crusted with bone ; (2) Lem^ospondijli, or those with the verte- 

 brae in separate bony pieces ; (3) Stereospondyli, or those with perfectly ossified vertebn^. 

 There is, however, good reason to believe that this arrangement is somewhat arbitrary and 

 provisional, and a number of imperfectly known species cannot be placed with certainty in 

 either group. The Canadian genera may all be arranged in two families, Microsauria and 

 Dendrerpetonîdœ.^ It may be remarked, however, that the former may prove to be entitled 

 to the rank of an order; and that in the case of the latter, the species included in it approach 

 so nearly to the Labyrinthodonts that they have hitherto been included by nu' in that family, 

 into which, indeed, the}' appear to graduate. 



Class— AMPHIBIA. 



Order — Stegocephala. 



Family — 3Iicrosauria, - Dawson. 



The Microsauria are lizard-like in form, with limbs usually well developed and five toes, 

 and a long but not flattened tail. Cranial l)oncs smooth. Maxillai'y and niandilmlai- teeth 

 numerous, simple. In some many small vomerine or palatal teeth. A'crtebne ossified 

 externally, bi-concave, with well developed articular, spinous, and in tlie trunk, lateral jiro- 

 cesses, ribs long and curved, generally with two heads, chest and abdomen protected by a 

 sternal plate and by bony scales or rods. Skin above with horny scales sometimes developed 

 into tubercles, spines or lateral lappets. 



Genus Hylonomus, Dawson. 



Teeth numerous, small, conical, sharjily pointed, vomerine teeth small and luimerous, 

 skull ovate, smooth ; hind limbs and pelvis remarkably wxdl developed; tail long, abdominal 

 scales oval. In some species an ornate arrangement of tubercles and spines on the back 

 and lapipets on the sides. 



' Zittel, Palseontologie, 1893, uses the term Gastrolepidoti ; but as the Microsauria also have abdominal bony 

 scales, this is not distinctive. 



^ Order Microsauria of my " Air-breathers of the Coal Period," 1863. I still think these animals ordinally 

 distinct. 



Sec. IV, 1894. 10. 



