262 Louis Dollo—On the Humerus of Euclastes. 
as a subfamily, my Pachyrhynchyna@,' did not their peculiar humerus 
show us a type having limbs wholly different from those of the 
Chelonide, and even to such a degree that, on account of them, it is 
necessary to create a distinct family, the Propleuride of Mr. KH. D. 
Cope.” 
III.—We will now proceed, more in detail, to the study of the 
humerus in question : 
1. To show, first, that it is really more chelydroid than chelonoid ; 
2. Then, as it might be doubted, we shall demonstrate that it really 
belongs to the Turtle to which we ascribe it ; 
3. Lastly, we shall draw from our observations the conclusions to 
which we shall be led, notably with regard to Phylogeny. 
IV.—To begin with, we shall compare the humerus of Chelydra 
to that of Chelone; we shall find :* 
CHARACTERS. CHELYDRA (Fig. 1). CHELONE (Fig. 3). 
7 Elongated, sigmoid. Section, at | Less elongated, rectilinear. Sec- 
Generaltcorm the narrowest point, distally to tion, at the narrowest point, dis- 
i processes, elliptic, but differing tally to the process, more or less 
slightly from a circle. elliptic, but very flattened. 
Heed Longest axis very oblique on the | Longest axis perpendicular to the 
PEIN longest axis of the distal end. longest axis of the distal end. 
(g:) 
HR Hardly rising above the head, whez | Rising very much above the head, 
Mesial process. the longest axis of the humerus when the longest axis of the 
(z.) zs vertical, humerus is vertical. 
ce Clearly detached fi e 
y detached from the head and 
Lateral process. | Placed close to the head. placed nearer to the distal end. 
(2.) 
Placed close to the head, with the | Less well circumscribed, oblique, 
5. longest axis perpendicular to the with the greatest axis nearly direc- 
Intertubercular longitudinal axis of the humerus, ted according to the longitudinal 
fossa. and wedged in between the lateral axis of the humerus, extending 
and mesial processes. towards the distal end. 
6. Well marked, and forming nearly | Forming hardly half the distal end 
Caos the whole of the distal end of the of the humerus; displaced me- 
a, 6.) humerus. sially. 
awe Much more developed; i 
ped; it causes the 
Bice ak Hardly developed. condyles to be displaced mesially. 
Teetic nd lar Present, but placed nearer to the 
eae Missing ; replaced by a groove. longitudinal axis of the humerus 
(e.) i than the groove of Cheljdra. 
V.— But: 
1. By its general form ; 
2. By its head ; 
3. By its mesial process ; 
(Fig. 2.) 
4, By its lateral process ; 
5. By its intertubercular fossa ; 
1 L. Dollo, ‘‘ Premiére Note sur les Chéloniens landéniens (Eocéne inférieur) de 
la Belgique,” Bull. Mus. Roy. Hist. Nat. Belg. t. iv. 1886, p. 139. 
2 KE. D. Cope, ‘‘ Synopsis,” ete., p. 235. 
3 L. Dollo, ‘‘ Chéloniens oligocénes,”’ etc., p. 78. 
