208 NEW YORK STATE MUSEUM 



finger is partially crossed by a bony process jutting out from the 

 former bone [fig. 58. ip]. It is connected with the insertion of the 

 extensor carpiuhiaris. 



This is the ind'icial process of the present writer. It appears on 

 the loth day in the chick of the fowl, being preformed in true 

 cartilage ; and it may or may not have a separate center of ossifica- 

 tion. By some it has been considered a rudimentary metacarpal of 

 an aborted middle finger, but its morphology is not as yet quite 

 clearly made out. There are still other vestigial ossifications in the 

 manus of the fowl, which also probably occur in the Tetraoninae 

 generally. Some of these have also been described by Parker in 

 the memoir from which we have been quoting, and are well worthy 

 of the examination of the comparative embryologist. 



In speaking of the phalanges, Parker further says : 



Passing to the young fowl, three c[uarters of a year old, we find 

 the distal phalanx of the pollex now forming the bony core of a 

 claw. • That of the index is a mere rough point, without a separate 

 bony center, and that of the third digit has disappeared. 



In the partridge, on the fourth or fifth day of incubation, a claw 

 is also to be seen on the distal phalanx of the pollex, which, how- 

 ever, is unossified. 



In the ripe embryo of the quail, the claw of the pollex is dis- 

 tinct ; the distal phalanx of the index is scarcely separate ; and the 

 third digit has only a single phalanx. 



In the ripe embryo of G a 1 1 u s s o n n e r a t i i , the distal 

 phalanx of the pollex is a well developed ungual hook, with a horny 

 sheath or claw. 



In the turkey (embryo, half ripe), the distal segment of the pollex 

 has a spatulate form, which form in P h a s i a n u s versicolor 

 (two fifths ripe) appears as a subcircular disk. In the latter species 

 the distal segment of the second digit is also an oval flat plate of 

 cartilage. This state of things, with more or less dilatation of the 

 distal segment before the nail sheath is developed, is constant in the 

 Carinalae. 



Still more interesting is the study of the embryonic skeletal 

 pectoral limb of the Ratitae, and Parker has not a little to say upon 

 that subject in the memoir we have been quoting. 



Coming next to consider the skeleton of the pelvic limb, I have ob- 

 served that the femur in the young chick of Centrocercus shows but 

 slight ossification on the third or fourth day; above, the head is 

 almost entirely in cartilage, while distally, the condyles are very in- 

 distinct and the bone exhibits no signs of pneumaticity. As the 

 bird grows, however, ossification rapidly progresses, and when the 

 individual is a month old, the salient characters of the bone can 

 easily be made out. 



