THE AMERICAN COAL MEASURES BRANCHIOSAURID^E. 55 



The position of the ribs in the matrix inclined backwards, and, making a small angle 

 with the vertebral column, is very suggestive of the condition in Branchiosaurus. 



The pectoral girdle is represented by three distinct elements of the left side, 

 which are identified as scapula, clavicle, and coracoid, following the nomenclature 

 given by Woodward (631), although Credner (186) would name them otherwise. 

 The scapula is represented by an ovoid fragment lying next to the vertebral column. 

 The clavicle was probably spatulate, as in Melanerpeton, but the inner end of the 

 element is not visible. The coracoid is represented by its outer end only, and its 

 inner pointed extremity is not visible. The interclavicle has not been detected. 



The himierus lies somewhat to one side of the pectoral girdle, as if there had been 

 a large amovmt of epiphyseal cartilage. Its position may be due to post-mortem 

 shifting, but there is little other evidence of any movement after deposition. The 

 humerus is a large, heavy bone in comparison with the rest of the skeleton. It is 

 expanded at each end, and its ends show concavities, proving that the bone is formed 

 principally of perichondral tissue, as would be expected from such an early Branch- 

 iosaurian. The endochondrium has not yet developed in this form, which is evi- 

 dently adult. There is no other element of the arm present. 



There is but a single element of the pelvis preserved, a slender elongate rod 

 which is undoubtedly the ilium, since it has the usual position for that element and 

 is much too large for a sacral rib. It has much the same shape as the ilium in the 

 modem Salamandra, and is not expanded as is the ilium of Branchiosaurus. This 

 element, like the humerus, seems to have been but a hollow cylinder of bone and 

 undoubtedly had cartilaginous ends, as in the ilium of the recent Salamandra. The 

 two femora are preserved nearly entire, the right one lying upon and partly obscuring 

 the sacral vertebra. The femur is much more slender than is the humerus, with 

 slightly expanded ends, and, like the humerus, shows the concavities at the ends, 

 indicative of the perichondral character of the tissue composing it. There are 

 two elements of the leg preserved more or less entire. The larger bone may repre- 

 sent the tibia and the smaller the fibula. They both present characters similar to 

 those of the femur and humerus. They are simple rods of bone tapering at the distal 

 end. The feet have been lost, though doubtless they were present at one time. 



The ventral surface of the body, as in other members of the Branchiosauria, was 

 covered and protected by a series of small scutes arranged in the regular chevron 

 pattern. The form of the scutes and their number can not be determined. The lines 

 which represent them are, however, distinct. Some of the scutes are missing and 

 some of them are obscured by lying over the vertebral column. They are all 

 somewhat shifted to the left. The lines are very small and close together. I count 16 

 of them in a distance of 2 mm. In length the longest line preserved is a little more 

 than 4 mm., measuring from the point of the chevron. The lines representing the 

 scutes come to a point in a median ridge which is now represented by a line. The 

 dermal scutes on the abdomen were probably the forerunners of the abdominal ribs 

 of the reptiles (fig. 9), 



The impression of the tail contains some of the most interesting features in the 

 entire specimen. Scattered over it and in places laid in mosaic are impressions of 



