1870.]-. HANCOCK AND-HOWSE—MARL-SLATE PROTEROSAURI. 571 
an inch thick, and the proximal extremity is nearly double that 
thickness, the increase being due in part to a ridge, apparently at 
the outer or upper surface. 
' The tibia and fibula are 1,1, inch long, so that they are a little 
more than 3 of an inch shorter than the femur. They are nearly 
straight ; the fibula is slender, and does not seem to have been much 
enlarged at the extremities, which are, however, not perfect. The 
tibia is considerably stouter, but not by any means so thick as the 
femur. The distal end is gradually thickened a little, but the prox- 
imal extremity is considerably and rather suddenly enlarged. In 
this, as in all the other bones, the articular extremities, having been 
formed of cartilage, are wanting, the ends being truncated. It is 
therefore quite impossible to describe in detail the characters of the 
joints. 
Fragments, apparently of the right tibia and fibula, and three or 
four of the phalanges, are scattered about in the vicinity of the 
bones of the left leg ; ; but no other traces of the right limb are to be 
“found, 
The only portion of the oe girdle present is the extremity of a 
flat bone. This fragment is =3, of an inch long, and vo of an inch 
wide ; it shghtly widens towards the anterior extremity, which is 
From the above description it seems evident enough that this 
small reptile is a true Proterosaurus, and that it is specifically di- 
stinct from P. Speneri. The long articulating limbs and extensively 
produced tail are common to both species. In both, too, the neck 
has been of considerable length, and the number of cervical vertebree 
(seven) is apparently the same in both. And the number of the dorsal 
vertebrae would likewise appear to agree in both species, and in each 
there are numerous ventral ribs. The same harmony is found in 
the number and character of the hand-bones. Unfortunately no 
comparison can be instituied respecting the skulls and the individual 
features of the vertebre, as these parts in the new species are too 
imperfectly preserved ; enough, however, seems to be known to war- 
rant the assertion that the two are generically coordinate. 
It appears equally clear that the small individual is specifically 
distinct. The diminutive size alone suggests this, especially as there 
are no appearances of immaturity; and the form of the ribs would 
seem to prove its specific distinctness. In P. Huxley: we have seen 
that they are flattened towards the proximal extremity, while in P. 
Spenert they are roanded at this part; and in the former they are 
not widened and grooved to any thing like the same degree at the 
distal extremity. 
The limbs, too, are proportionately different. In P. Speneri the 
fore limb is AL inches long, as figured in yon Meyer’s work, tab. 2S 
The hind limb is 72 inches in length ; consequently the former is 3 
shorter than the latter. In P. i wccler yt the fore limb is 155 inch in 
length, the hind limb 22 inches long; the former in this species 
therefore considerably more than 2 the length of the latter. 
In the new species, then, the limbs yary more in length than they 
252 
