S. W. Williston — Restoration of Limnoscelis. 4(53 



alous, the articulation continuous from head to tubercle, unless 

 those of the atlas and axis are exceptions. The axis has a short 

 rib, forty-two millimeters in length, with a width of eighteen 

 at the extremity. The third rib is about sixty-five millimeters 

 in length, and has a distal width of forty. The fourth is sev- 

 enty-five millimeters in length, with a distal width of about 

 sixty. It is this rib which was figured by me in my cited 

 work, page 36 and plate xxxvm, as a probable hyoid. The 

 fifth rib is scarcely longer than the preceding one, but is 

 broader at the extremity, and the sixth rib, of the same length, 

 is even more expanded at the extremity (fig. 11). These ribs 

 are all thin at the distal extremity and somewhat concave on 

 the inner side. In specimen 811 (fig. 10) the vertebrae lie in 

 position over the pectoral girdle. In settling down, after de- 

 composition of the body had begun, these broad-ended ribs 

 were dragged upward, especially on the right side ; all four, 

 that is of the third, fourth, fifth and sixth vertebrae, lie on the 

 inner side of the scapula ; the rib of the axis on the left side 

 just underlaps the margin of the scapula. It is very evident 

 that the function of these peculiarly expanded ribs was for the 

 attachment and support of the scapula ; in other words, they 

 served the same purpose for the pectoral girdle that the sacral 

 ribs did for the pelvic, and it is evident that their union 

 was nearly or quite as firm. They may properly be called 

 notarial ribs, and their supporting vertebrae notarial vertebras. 

 These dilated and shortened ribs are more or less characteristic 

 of all American Cotylosauria, and, in a less degree, of Ojohi- 

 acodon, an American pelycosaur. 



The seventh rib has nearly the full length of those succeed- 

 ing, but is unusually stout and broad, especially distally. The 

 following ribs are more slender ; they all lie in position in the 

 holotype, and their relative lengths, with the necessary fore- 

 shortening, I have endeavored to show faithfully in the restor- 

 ation. The length of the seventh rib, measured on its chord, 

 is five and three-fourths inches ; of the eighth and ninth, six 

 inches ; of the fifteenth, five and three-fourths inches ; of the 

 eighteenth, three and one-half inches. 



The single pair of functional sacral ribs are of the usual dia- 

 dectid type, flattened and expanded distally and directed down- 

 ward, lying in apposition, but not suturally united, with the 

 inner side of the ilium above the acetabulum. The ribs of the 

 second sacral, or sacrocaudal, vertebra are much less stout than 

 the following ones. The first true caudal ribs are elongate, 

 curved outward and backward, lying inside the posterior pro- 

 longation of the ilium for the most part; they terminate appar- 

 ently in a pointed extremity. The second pair of ribs are 

 extraordinary. In specimen 819, where they are preserved 



