10 R. W. Shujeldt 



Professor Marsh nowhere in the article states whether this bone 

 came from the right or the left pelvic limb. From the fact, however, 

 that he speaks of the "outer metatarsal," he apparently recognized 

 that the bone was from the right side, which is the case. This outer 

 metatarsal is, however, not "double the size of the third," but is 

 simply one centimeter longer than the third, or has exactly the same 

 length as the middle metatarsal. 



With respect to the proximal piece, which is evidently from a ver}' 

 young bird, ossification has not proceeded sufficiently far to have 

 formed "canals or grooves for tendons" on the posterior aspect of 

 the bone. As a matter of fact, when present, they are not found until 

 complete development and ossification has culminated, as we find it 

 in the fully matured individual. In Gavia immer the groove is narrow 

 and sharply defined for the lower half of the posterior aspect of the 

 shaft of the tarso-metatarsus in the adult bird, being shallower and 

 broader above. These grooves, however, are always present in this 

 locality on the tarso-metatarsi of all powerful swimming birds and 

 divers. 



To me, there is a lack of clarity in Professor Marsh's description of 

 this material, and especially in what he says in regard to its agreement 

 with the tarso-metatarsus of Hespcrornis. Both these birds were 

 powerful divers but utterly different forms. He states that "This 

 specimen indicates a bird about a large as a loon and apparently of 

 similar habits. The locality of the remains at present known is in 

 Western Kansas, in the same cretaceous beds that contain the Odon- 

 tornithes and Pteronodonliay 



I have carefully compared these two fragments of Marsh's " Baptor- 

 nis advenus^' with the corresponding bone in both Gavia immer and 

 Hesperornis regalis, and I am of the opinion that the specimen belonged 

 to a diver related, on the one hand, to the Hesperornithidce, and on the 

 other to the existing Pygopodcs, perhaps — ^though by no means 

 certainly so — to a family group in which Gavia belongs, that is, so far 

 as its affinities are concerned, it was no nearer the one than the other. 

 Our Loons {Gavia) are descendants from hesperornithine stock, and 

 this Baptornis advenus of Marsh, although from the Cretaceous of 

 Kansas, may not have been so nearly related to Hesperornis as he 

 inferred. It was doubtless larger, perhaps ivhen adult considerably 

 larger, than the present Gavia immer, as I believe it to have been; but 

 whether it possessed teeth or not we have, as yet, no evidence. 



As in other existing divers among the Pygopodes, there is very 

 marked trans\^erse compression of the shaft and distal extremity of 



