PRIMITIVE REPTILES 655 



Datheosaurus macrourus Schroeder. This genus and species 

 from the lower Rothliegende of Germany, is unfortunately known 

 only from a single specimen, not in the best preservation. It is 

 a very slender reptile with a very long tail, with no known char- 

 acters at variance with the preceding lists. Doubtless the 

 interclavicle has an elongated stem and the humerus an entepi- 

 condylar foramen. Whether the temporal region is perforated or 

 not is not known. In other characters, especially the structure 

 of the vertebrae, it is sharply excluded from the Cotylosauria. 

 Its nearest relationship seems to be with Kadaliosaurus, Arae- 

 oscelis and Paleohatteria. 



MICROSAURIA 



The name Microsauria was first proposed by Dawson in 1863^^ 

 based upon Hylonomus, a genus described by him from the 

 carboniferous of Nova Scotia. Nearly thirty years later, Credner 

 described^^ more fully and in detail another species, H. geinitzii, 

 from the middle Rothliegende of Germany, which he referred 

 to the same genus, together with an allied new genus and species, 

 Petrobates truncatus from the same horizon. In 1897, Baur^" 

 expressed the opinion that both forms were, in reahty reptiles as 

 Credner had suspected: 



Die Frage ob Hylonomus und namentlich ob Petrobates den Stego- 

 cephalen oder aber den Rhynchocephalen zuzurechnen seien, lasst sich 



nicht durch ein kurzes Wort entscheiden Wenn man bei 



Petrobates vom Schadel absieht, welche nicht genau genug bekannt ist, 

 so konnte man diesen Vierfiissler fiir einen kleinen Rhynchocephalen 

 aus der Familie der Proterosaurien halten, wenn dem nicht das Vor- 

 handensein von nur einen Sacral-wirbel entgegenstiinde.-^ 



I scarcely doubt but that had Credner known of stegocrotaphic 

 reptiles with a single sacral vertebra, such as Diadectoides and 



'^ "My first impression is that they constitute a separate family or order, to 

 which I would give the name Microsauria, and which may be regarded as allied, 

 on the one hand, to certain of the humbler lizards, as the Gecko or Agama, and 

 on the other to the tailed Batrachians." Air breathers of the coal period, p. 47. 



i» Zeitschrift der deutschen geologischen Gesellschaft, Bd. 42, p. 241, 1890. 



20 Anat. Anz., Bd. 14, 



21 Credner, op. cit., p. 257. 



