640 
DR. J. W. DAWSON - ON ERECT TREES CONTAINING ANIMAL 
very large and stout, nearly as long as the mandible ; leg bones and phalanges 
correspondingly stout. 
The thoracic plate is indicated only by some fragments. The abdominal scales are 
narrow and pointed (oat-shaped), smooth externally and with a ridge at one side 
within. 
The following are dimensions of the largest specimen :— 
Length of mandible 
„ largest tooth . 
„ femur 
„ tibia . 
„ humerus 
„ radius . 
,, vertebra 
rib 
scales 
4’4 centimetres. 
5 millimetres. 
3‘5 centimetres. 
6 millimetres. 
3 centimetres or more. 
5 to 7 millimetres. 
Under the microscope the bone presents a coarser structure than that of Hylonomus, 
the bone-cells being large and of elongated form. The dentine of the teeth has coarse 
tubes with canaliculi, the appearance being very similar to that in Smilerpeton, though 
the tubes are scarcely so large. 
It seems evident that Hylerpeton Dawsoni was an animal somewhat stout and 
broad in form, with a large and pointed head and massive limbs. It seems to have fed 
in part at least on Millipedes, as remains of these are found in coprolite associated 
with its bones. For some reason also, the specimens of this species seem to have been 
among the earliest introduced into the erect trees. Perhaps they sought their myria- 
podous food near these hollow trunks, or were in the habit of breaking up decayed 
wood in search of Myriapods. 
7. Hylerpeton longicle)datum, s.n. (Plate 42, figs. 86 to 109). 
[Preliminary Notice, American Journal of Science, December, 1876.] 
Two specimens of the species occur in the collections, neither of them perfect. 
Their characters warrant us in placing the animal in the genus Hylerpeton , but it is very 
distinct from the previous species, more especially in the length and slenderness of its 
teeth, and in the breadth of its thoracic plate. 
Head much elongated, with the bones minutely pitted, and with delicate microscopic 
striae, but not sculptured. Mandibular and maxillary teeth long and acute, pointing 
backwards, with the apex of their inner sides finely striated ; twenty or more in each 
ramus of the lower jaw; palatal bones with several long slender teeth and many 
