146 Sir J. W. Dawson — On Dendrerpeton Acadianum, etc. 



Vertebrae imperfectly ossified, very slightly biconcave, with large 

 and broad neural processes in dorsal region. Those of the tail have 

 spines above and below. Eibs of moderate length, with expanded 

 head and slight shoulder; solid towards the head, but hollow and 

 thin-walled at distal end, the longest barely equal to the breadth of 

 the skull, curved, the anterior ones very much so, scapular and 

 pelvic bones large and well ossified. Ilium ? broad. 



Limbs well developed, especially the anterior pair. Limb-bones 

 ossified and cancellated at the extremities, and with bony walls of 

 considerable thickness. Humerus equal to more than half of the 

 length of the mandible. Femur smaller than humerus, the tibia 

 flattened at the extremity. Toes five in each foot, somewhat broad 

 and short. 



Chest covered with bony scales, which are thin, unequally ovate 

 and about half as wide as long, and marked with obscure concentric 

 lines. They have a thickened edge or margin interiorly. They are 

 arranged in chevron and close together, forming a compact armour. 

 There appears to have been a rhombic breast-plate in front, with 

 obscure radiating lines, but this has only been found detached. 



Skin of upper surface of body minutely granular or scaly, with 

 a semicircular patch of horny tubercles in front, which I have 

 referred to the snout, but it may have belonged to the back of the 

 head. On the throat or sides were flat, pointed, and apparently 

 flexible lappets marked with elongated areoles and pores. Nearly 

 the whole skin of some specimens has been preserved in the erect 

 trees apparently by a sort of tanning process, but it is so flattened 

 and crumpled that its form is scarcely discernible. 



The following are the dimensions of two specimens, one of them 

 (No. 2), that of 1890, and the largest yet obtained : — 



* The skulls being flattened and crushed, these measurements are not certain. 



In form, Dendrerpeton Acadianum was probably elongated and 

 lizard-like ; with a broad flat head, short stout limbs, and an 

 elongated tail ; and having the skin of the belly protected by small 

 bony plates closely overlapping one another, while the upper part 

 of the body was covered with a tough skin more or less scaly and 

 ornamented in parts with lappets or pendants. As in the case of 

 other small Reptilians of the Coal, its enemies were found rather 

 below than above. Its armour therefore was beneath. 



The bone-cells are broad and with much-branched canaliculi, those 

 of the bony scales being similar to those of the other bones. The 

 hollow bones are occupied with calcite stained brown and probably 

 representing cartilage. 



