1887.] ON A VESTIGIAL STRUCTURE IN THE OSTRICH. 2n3 



EXPLANATION OF THE PLATES. 

 Plate XX. 



Fig. 1 . Pi7nelodus hucJcleyi, p. 275. 



2. Pimelodus {Bhamdia) longioauda, p. 275. 



Plate XXI. 



Fig. L Pimelodus (Pseudojnmelodus) pulcher, p. 276. 



2. Sfygogenes humboldti, p. 276. 



3. Nannoglanii fasciatus, p. 278. 



4. Stegophilus punctatus, p. 279. 



Plate XXII. 

 Chcetostomus dermorhynchm, p. 277. 



Plate XXIII. 



Fig. 1. Parodon buckleyi, p. 279. 



2. Piabtioina elongafa, p. 280. 



3. Leptagoniates steindachneri, p. 282. 



Plate XXIV. 

 Sternarchus {Ehamphosternarchus) curvirostru, p. 282. 



3. Note on a Vestigial Structure in the Adult Ostricli repre- 

 senting the Distal Phalanges of Digit iii. By Richaeu 

 S. Wray, B.Sc. (Communicated by Professor Flower.) 



[Received February 2, 1887.] 



While examining an Ostrich's wing in the fresh state in order to 

 make out the relation of the quill-feathers to the bones, I was struck 

 by observing that the phalanx of the third digit had a large amount of 

 cartilage at its tip. Having another wing available with that part un- 

 injured, I removed the skin covering it, and carefully dissected out the 

 phalanx of digit in. From the tip of this there extends a round 

 band or rod of cartilage about half the length of the first phalanx ; 

 at its base it is as broad as the tip of the phalanx, at the other end 

 about one sixteenth of an inch in breadth. Its distal end fades into 

 the connective tissue in that region. When first dissected out, the 

 cartilaginous rod showed no signs of ossification ; but when placed 

 in glycerine, the rod became quite transparent, showing a free second 

 phalanx embedded in it, and occupying its proximal third (see fig. 1, 

 p. 284). 



The shape of the phalanx of digit in. is often as shown in fig 2, 

 the pointed end being the fused second phalanx, which in adult spe- 

 cimens may be free and embedded in cartilage. The adult Ostrich, 

 therefore, presents the nearest approach to the pentadactyle manus 

 among Birds. 



Through the kindness of Mr. G. B. Howes, I have had the oppor- 

 tunity of examining some fore limbs of Ostrich embryos. These (see 

 fig. 3) show a most interesting appearance, the outline of the digits is 



