376 Mr, T. Atthey on Pteroplax cornuta. 



number of bones entering into their formation than into those 

 oi Loxomma and Anthracosaurus, and the invariable absence of 

 the snout, maxillaries, and mandibles are the chief character- 

 istics of Pteroplax cornuta. The inferior parts of the skull 

 being also wanting in both our instances renders it probable 

 that Pteroplax had a skull much less completely ossified than 

 either of the two animals above named, and that it partook 

 more than they did of a batrachian or piscine character. 



That it had two pairs of limbs, feet or paddles, is very 

 probable, and that it was an air-breather is evidenced by the 

 form, length, and breadth of the ribs, and perhaps also by the 

 grooved state of the under surface of the frontal bones. 



Of its body we know nothing beyond the scanty vertebrae, 

 fragments of ribs, and scutes. 



If, with the desire to form soitiething approaching to a defi- 

 nite idea of the comparative size of our three Labyrinthodonts, 

 we suppose the length of the animal to be seven times that of 

 the skull, Avhich is about the proportion in Keraterpeton Gal- 

 vani (a comparatively short species), and if we allow two inches 

 for the lost part of the larger specimen of Pteroplax^ the skull 

 of this animal, from the end of the snout to the end of the occi- 

 put, will be 1\ inches long, and the whole length of the body 

 4 feet 8 inches. 



By the same rule of the body being seven times the length 

 of the head we find that Loxomma Allmanni, with a skull 

 12^ inches long, must have measured 7 feet 7 inches ; and in 

 like manner Anth7-acosaurus Busselli, with, a skull of 13^ inches, 

 must have had a total length of 8 feet 2 inches. The correct- 

 ness, however, of this rule is questionable ; and it is not easy 

 to say what was the length of the tail in each case. 



As was noticed in the ' Annals and Magazine of Natural 

 History ' for August 1876, the prgemaxilla figm-ed in a previ- 

 ous number as that oi Pteroplax^ and the teeth, as since shown 

 by an examination of their minute structure under the micro- 

 scope, as well as four or five fragments of mandibular bones, 

 which had been described as " most probably belonging to 

 the same large Labyrinthodont amphibian," all belong to 

 Loxomma Allman7ii ] whilst the vertebrge and sternal plates, 

 also figm-ed and described as belonging to Pteroplax^ are pro- 

 bably remains of Anthracosaurus Russelli. 



My acknowledgments are due to my friends Dr. Embleton 

 and Mr. William Dinning — to the former for his assistance 

 in the above description, and to the latter for the accurate and 

 beautiful drawings illustrative of that description. 



