784 ON A NEW BIRD FJiOM THE LONDON CLAY. [June 20, 



molluscs, or, in the case of the Frigate-bird, on what thej can take 

 from the G;innets and other birds. I never saw either really dive, 

 although they drop down to pick up food from the surface 

 of the sea, and on one occasion only I saw a Tropic-bird sitting 

 on the water. This being the case, it appears that the hind limbs 

 are scarcely used at all, and the reduction in size that has been 

 undergone by the pelvis and hind limb is no doubt correlated with 

 this disuse. In Frophaelhon both pelvis and hind limb seem to 

 have retained their normal relative size, and this bird was probably 

 a good swimmer and diver and resembled Sida and Phalacrocorax 

 both iu its habits and in its structure more nearly than does its 

 modern representative Phaethon, many of the peculiar characters 

 of which have been acquired since the Eocene. Nevertheless, 

 Phaethon presents many peculiarities which indicate that it is really 

 a somewhat primitive type, and probably the stock of which 

 Prophaethon and Phaethon are tiie middle and terminal members 

 branched off from the common stock of the Steganopodes at a 

 very early period, perhaps not later than about the beginning of 

 the Cretaceous. It is known that the group is a very ancient 

 one, tcr Marsh has described several species (Graculavus) which 

 occur in the Upper Chalk, and were regarded by him as almost 

 certainlv Stegauopodes which already show relationship with the 

 Cormorants. 

 The dimensions of the pelvis are : — 



millim. 



Total length as preserved 88 



"Width at antitrochanter 27 



Width at middle of pelvic escutcheon 15 



Length in front of antitrochanter 49 



Length of ischiadic foramen 25 



The dimensions of the femur are : — 



millim. 



Length (approximate) 52 



Antero-posterior width of outer surface of trochanter.. 11 

 Width of middle of shaft 5 



Conclusions. 



The conclusions arrived at from the examination of this 

 specimen may be summarized as follows : — 



(1) The structure and position of the quadrate and the form of 



the pelvis indicate that the fossil is a Steganopodous bird. 



(2) The form of the cranial region of the skull and of the 



rostral hinge, as well as some other points, indicate that it 

 is most nearly related to Phaethon. 



(3) The relatively large size of the pelvis and femur indicate 



that the bird more nearly resembled the ordinary Stegano- 

 podous type than does Phaethon, in which the pelvis and 

 bind limb are in a greatly reduced condition. 



