OCCURRENCE OF LOXOMMA ALLMANNI. 207 



specimens generically, and we believe specifically, is equally cer- 

 tain ; and that Pteroplax is distinct from Loxomma we have the 

 high authority of Prof. Huxley, who has examined our type 

 specimens of the former. 



This is quite evident even on a cursory examination of the 

 two forms. But we may take this opportunity to state that 

 Pteroplax deviates considerably, in the structure of the cranium, 

 from all known Labyrinthodonts. In the conformation of the 

 head it approaches the Siren. This fact was entirely overlooked 

 by us at the time of the publication of our paper on the subject 

 (Ann. Nat. Hist., Ser. 4, Vol. I., p. 266), and was not recog- 

 nised until Prof. Huxley kindly pointed it out to us some time 

 afterwards. 



Pteroplax has no posterior lateral expansions like those in 

 Anthracosaurus and Loxomma, as we thought it would have (the 

 whole, or nearly the whole, of the cranium is figured in plate 

 xv. fig. 1 of the above paper, and likewise in the Nat. Hist. 

 Trans, of Northumberland and Durham, Vol. III., pi. II.) ; the 

 maxillae are also deficient. The long curved horns are undoubt- 

 edly the equivalents of the lateral external cornua in Loxomma; 

 and the overlying points are the homologues of the inner horns, 

 being in both genera the posterior extremities of epiotic bones. 



Shortly before the occurrence of the cranium of Loxomma at 

 Newsham, Mr. Atthey obtained from the same locality a series 

 of vertebrae, lying nearly in natural order, with a few ribs scat- 

 tered among them. We think these also probably belong to 

 Loxomma. There are fourteen or fifteen vertebrae ; but, unfor- 

 tunately, little can be made out respecting them except the form 

 and character of the bodies, the processes of which are not de- 

 terminable, though they seem mixed up with the matrix, which 

 is partly composed of iron-pyrites. 



The largest vertebras are about seven-eighths of an inch wide, 

 and five -eighths of an inch long ; they are slightly hollowed at 

 the ends, with the margins a little reflected ; there is a minute 

 notochordal foramen in the centre, but this is not always visible ; 

 and the sides are hollowed or channelled, but do not exhibit 

 much striation. 



