510 HARRY GOYIER SEELEY ON THE 



sures T 5 ^- inch from front to back ; and the outer one is nearly as 

 long. The inner articulation is placed about this height above the 

 middle one, and is more compressed from side to side than the others, 

 but measures as much from front to back ; it terminates posteriorly 

 in a sharp ridge, which is prolonged up the bone. The inner ele- 

 ment of the metatarsus is thrown behind the middle bone, so as to 

 be very imperfectly seen from the front. 



So far as I have seen, no digital bones have been collected. 



These remains offer evidence of many parts of the skeleton in at 

 least two species of birds, distinguished from each other by size and 

 minor osteological characters : the larger, here named Enaliornis 

 Barretti, is indicated by skull, vertebral column, pelvis, and all the 

 larger bones of the hind limb ; the smaller species, Enaliornis Sedg- 

 wicJci, is at present only known by its dorsal vertebras, femur, tibia, 

 and metatarsus. 



Although some of the bones and parts of the vertebral column in 

 both these species sometimes show evidence of remarkable persistence 

 of cartilaginous conditions of the articulations, especially in the region 

 of the dorsal vertebrae, I do not find this character to suggest that 

 the animals should not, in classification, be placed along with existing 

 Natatorial birds, with which all their other osteological characters 

 closely associate them. Even if these Greensand fossil birds should 

 hereafter prove to have had teeth like Ichthyornis and Hesperornis, 

 I should be inclined to remember the variableness of dental and 

 other characters in the existing orders of Mammals and Reptiles as 

 a reason for more than hesitation before contemplating the removal 

 of these Cretaceous fossils from the Natatorial section of the class 

 Aves. When the affinities of the fossil type to Colymbus are so per- 

 sistent, both in the English and American genera, the biconcave 

 condition of certain vertebrae seems to be of no more value than 

 the opisthoccelous condition of dorsal vertebrae in the Penguins ; and 

 the toothed condition of jaws I should estimate in classification by 

 our knowledge of dental variation observed in the j aws of Monotre- 

 mata and Edentata, and conclude that the character is only generic. 



Besides thanking the gentlemen whose assistance has been already 

 mentioned, I would express my thanks to Professor T. M'Kenny 

 Hughes, E.G.S., for the kindness with which he has permitted me 

 to make use of the resources of the Woodwardian Museum, and 

 figure the specimens referred to in this and other papers. 



EXPLANATION OF THE PLATES. 



Plate XXVI. 



Fig. 1. Right side of occipital and parietal regions of the cranium of Enaliornis 

 Barretti in the Woodwardian Museum. 



2. Anterior view of the same specimen, showing a section of the cerebral 



cavity. 



3. Posterior view, showing the foramen magnum and occipital bones. 



