Sir J. W. Daicson — On Dendrerpeton Acadianum, etc. 153 



that it raay have been in the habit of sitting erect. The thigh-bone 

 is well formed, with a distinct head, and the lower extremity flattened 

 and moulded into two articulating surfaces for the tibia and fibula, 

 the fragments of which show that they were much shorter. The 

 toes of the hind-feet have been seen only in detached joints. They 

 seem to have been thicker than those of the fore-foot. Detached 

 vertebrae, apparently caudal, have been found, but the length of the 

 tail is unknown. The limb-bones are usually somewhat crushed 

 and flattened, especially at their articular extremities, and this 

 seems to have led to the error of supposing that this flattened 

 form was their normal condition ; there can be no doubt, however, 

 that it is merely an eifect of pressure. The limb-bones present in 

 cross-section a wall of dense bone with elongated bone-cells, sur- 

 rounding a cavity now filled with brown calc-spar, representing 

 cartilage. Nothing is more remarkable in the skeleton of this 

 creature than the contrast between the perfect and beautiful forms 

 of its bones, and their imperfectly ossified condition, a circumstance 

 which raises the question whether these specimens may not repre- 

 sent the young of some reptile of larger size. 



The dermal covering of this animal is represented in part by 

 oval bony scales, which are so constantly associated with its bones 

 tliat I can have no doubt that they belonged to it, being the 

 clothing of its lower or abdominal parts ; while above it was clad 

 in the beautiful scaly covering above described. The scales are 

 thicker than those of Dendrerpeton. On the inner side they are 

 concave, with a curved ledge or thickened border at one edge. On 

 the outer side they present concentric lines of growth. The com- 

 panion genera above named are not known so completely as Sylono- 

 miis, but all their characters so far as known would place them with 

 it as members of the same group rather than with Dendrerpeton and 

 its allies. Of other American forms it appears to me probable that 

 Saiiropleura digitata of Cope ^ may be very near to my genus Fritschia, 

 and agrees with it in having rod-like abdominal scales, but its 

 head is not yet known. Bracliydectes of the same author is very 

 near to Ifylerpeton, especially as specimens of the latter recently 

 obtained show some characters, as the ascending ramus of the lower 

 jaw, on which Cope distinguishes this genus. 



Of Fritsch's species several raay come within the group of Micro- 

 sauria. The genus Hyloplesion of this author has indeed been united 

 by Credner with Sylonomus, a position to which it scarcely seems 

 entitled, and Petrohates of Credner is nearly allied, while Seelya and 

 Dawsonia of Fritsch also approach to the characters of this order. 

 Still the whole of these animals seem very inferior in development 

 of limb and form of body to Ilylonomus. 



I regret very much that, owing, as I believe, to imperfection of 

 material, so many palaeontologists have failed to appreciate fully 

 the characters of Eylonomus as a type of the higher Carboniferous 

 Amphibia approaching to Reptilia. 



Fritsch, in the conclusion of his important work on the Stego- 

 ^ Ohio Eeports, vol. ii. p. 388. 



