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Show 887.] ON A VESTIGIAL STRUCTURE IN THE OSTRICH. 283 EXPLANATION OP THE PLATES. PLATE XX. Fig. 1. Pimelodus buckleyi, p. 275. 2. Pimelodus (Rhamdia) longicauda, p. 275. PLATE XXI. Fig. 1. Pimelodus (Pseudopimelodus) pulcher, p. 276. 2. Stygogenes humboldti, p. 276. 3. Nannoglanis fasciatus, p. 278. 4. Stegophilus punctatus, p. 279. PLATE XXII. Chcetostomus dermorhynchus, p. 277. PLATE XXIII. Fig. 1. Parodon buckleyi, p. 279. 2. Piabucina elongata, p. 280. 3. Leptagoniates steindachneri, p. 282. PLATE XXIV. Sternarchus (Bhamphosternarchus) curvirostrit, p. 282. 3. Note on a Vestigial Structure in the Adult Ostrich representing the Distal Phalanges of Digit in. By RICHARD S. W R A Y , B.SC. (Communicated by Professor FLOWER.) [Eeceived 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 uninjured, 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. W h e n 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 specimens 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 M r . G. B. Howes, I have had the opportunity of examining some fore limbs of Ostrich embryos. These (see fig. 3) show a most interesting appearance, the outline of the digits is |
