636 
DR. J. W. DAWSON ON ERECT TREES CONTAINING ANIMAL 
Anterior limb slender, humerus with distinct keel; radius and ulna separate; toes, 
four or five. 
Posterior limb with well-developed femur, with a trochanter and bifid articulatory 
surface at distal end; tibia and fibula shorter, separate; toes five, somewhat long and 
slender. 
Pelvis large, principally composed of two large broad triangular ilio-ischiac bones. 
Tail probably shorter than the body; thirteen vertebrae seen in one specimen. 
Lower surface protected with a thoracic plate and numerous oval bony scales, with 
delicate lines ot growth externally, and concave internally with thickened edges. 
Upper surface protected with imbricated horny scales. In front two rows'of horny 
tubercles and plates, with epaulettes composed of bristle-like fibres projecting from the 
skin (Plate 39, fig. 2? ; Plate 45, fig. 140). 
The dimensions of the largest individual found are as follows: — 
Length of head . 
about 2 centimetres 
i) 
neck. 
» P3 
}> 
trunk. 
,, 7 
>> 
posterior limb to heel 
.... 3 
S3 
mandible .... 
■> 
00 
r—1 
• 
• 
S3 
lib. . 
. . . . P3 
5 3 
humerus .... 
ss 
femur . 
.... 1-8 
ss 
tibia . 
.... 1*2 
5) 
body of vertebra . 
. . . . 2*5 millimetres. 
Teeth, five in 1 millimetre. 
A smaller individual gave the following measurements 
Length of mandible 
j, rib v 
„ humerus 
,, femur . 
7 millimetres. 
6 
5 
7 
SS 
Under the microscope the bone of Hylonomus Lyelli shows well-marked cells and 
canaliculi, the cells being oval in the cranial bones and more elongated in the limb 
bones. The dentine of the teeth presents very fine tubes radiating from the pulp 
cavity, and covered with a thin plate of structureless enamel at the outer surface. 
In such specimens of this animal as are preserved in sufficient perfection to show its 
attitude, the head and trunk lie on one side, showing that the body was compressed 
laterally; a form fitting it to pass among dense vegetation. Coprolitic matter associated 
with its remains contains fragments of insects. 
