Fossil Birds in ihe Marsh Collection of Yale University 51 



about as large as the Golden-winged woodpecker {Colaptes auratus 

 Sw.)." He then completes his account by adding a technical 

 description of the specimen and some measurements of it. 



So far as his description of the specimen is concerned, it would 

 appear to be quite correct, and I dare say his measurements are, too, 

 although I have not verified them. When we come, however, to 

 compare this fossil specimen with the right tarso-metatarsus of 

 ''Colaptes auratus,^' or any other true woodpecker like it, the fact will 

 at once be recognized that Professor Marsh was not at all justified in 

 referring his Uintornis lucaris to the Pici, and I am inclined to beHeve 

 that it was a species in no way related to them. 



On account of its being a zygodactyle foot, or a foot belonging to 

 a " Scansorial" bird (as Marsh defined it), it has long been known that 

 that type of foot presents some very interesting modifications over 

 the foot in an ordinary passerine bird. In the woodpecker's foot, the 

 first toe is the shortest, it being the inner posterior one; the second toe 

 is the next longest and is the inner anterior one; the third toe, or 

 outer anterior one, is still longer, and, finally, the fourth toe, or outer 

 posterior one, is in nearly all woodpeckers the longest of all the toes. 

 This unusual scansorial arrangement calls for a peculiar modification 

 of the trochlear processes of the tarso-metatarsus, and this modifica- 

 tion is recognizable on sight. Briefly, it may be said that the fourth 

 or outer posterior toe, in so far as the basal phalanx of it is concerned, 

 in the skeleton of the foot, has had a remarkable modification take 

 place in the trochlear process of the tarso-metatarsus with which it 

 articulated. This, as we would expect, has become bifid, twisted 

 around posteriorly, in part, the posterior process having become 

 double the size of any of the other prolongations. 



Marsh's Uintornis lucaris presents no such feature or modification, 

 and consequently the bone did not belong to a woodpecker. 



It did not come from a typical passerine form of bird; for in the 

 Passeriformes, as a rule, the trochlear projections are nearly parallel 

 to each other, while in this specimen, as Marsh pointed out, they are 

 " divergent." This cuts out a large group, and the probability is that 

 it was not a passerine species. 



All the zygodactyle birds exhibit some such modification of the 

 trochlear processes of the tarso-metatarsi as do the woodpeckers; and 

 this sets aside another formidable array of forms, no one of which it 

 can be referred to, as the parrots, toucans, cuckoos, etc. We still 

 have the Cypseli, the Caprimulgida, the Kingfishers, and numerous 

 other non-passerine birds, with which it should be compared. This, 



