20 ON THE STRUCTURE OF EUSTHENOPTERON 
narrow elongated bone, and from its lower margin arises a pro- 
cess which articulates with the cleithrum. The cleithrum is the 
largest element of the girdle and externally overlaps the clavicle, 
a triangular element with no upwardly ascending process such 
as has been found in Rhizodus. The scapulo-coracoid is a rather 
small element tapering behind where it is abruptly thickened. 
Its posterior face is excavated to articulate with the single prox- 
imal piece of the limb which Broom, Gregory and others consider 
to be homologous with the humerus of the tetrapoda. This 
scapular element is, indeed, somewhat like that in Polypterus, 
except, that the coracoid is apparently not a distinct bone. On 
Plates 11 and 12 I have illustrated the left pectoral fin, with its 
skeletal supports. Fig. 1 on Plate 12 shows the best specimen 
of this fin I have ever seen and, fortunately, most of the elements 
of the right pectoral are preserved in the same specimen. 
It is seen by an examination of this fin that there are five axial 
pieces instead of the four shown in the British Museum example 
figured by Pietronievics; and three postaxial processes instead 
of two. These postaxial processes are certainly not distinct 
elements, the haversian canals leading up to the center of ossi- 
fication in the main body of the axinost. Neither do I find that 
the fourth axinost is bifucrated as supped by Pietronievics. 
It has a postaxial process as indicated in Broom’s figure and 
articulated to its main body distally is a fifth axinost. This, as 
well shown in its mate of the right side is small, robust, con- 
stricted in the middle; and a longitudinal groove like that in the 
second axinost shows interesting traces of the concentration of 
elements which has taken place in this fin; thus the mesomere 
thought by authors to represent the ulna is very evidently made 
up by the fusion of two or more elements. Fig. 2 on Plate 11 
shows the squamation of the fleshy lobe of the fin as well as the 
tubercular ornament of the scale-like rays. 
The endo-skeletal supports of the pelvic fin are not very well 
preserved in any of the specimens which have come under my 
notice. They have, however, been heretofore illustrated by 
Goodrich. Plate 13 shows the pelvic bones in their natural 
association behind which is a peculiar arrangement of a portion 
of the squamation which I assume marks the position of the 
vent. On Plate 1, fig. 2, may be seen a specimen which shows 
the supports of the dorsal and anal fins; and on Plate 12, fig. 2, 
