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Show 1880.] MR. W. A. FORBES ON LEPTOSOMA DISCOLOR, 467 birds as the Cuckoos, Parrots, or Toucans. In this spirit-preserved specimen it is easily demonstrable that the fourth digit cannot naturally be placed in a really reversed position, like that of the above-named birds. While the second and third toes look directly backwards, the hallux looks inwards and forwards, and the fourth toe inivards and slightly backwards at its apex, there being, as it were, a slight twist in its axis1. However much the fourth toe is bent backwards (and this is only done by the exercise of some little force), its plantar surface always looks more or less inwards. The presently-to-be-described arrangement of the deep plantar tendons also confirms the view here taken as to Leptosoma not being a true zygodactyle bird. Pterylosis.-As regards Leptosoma, Nitzsch only noted the presence of an aftershaft and 12 rectrices, he only having been able to examine a stuffed specimen. Mr. Sclater, in his above-mentioned paper, besides describing the two characteristic lumbar powder-down patches of this bird, briefly alludes to the pterylosis, which " appears nearly similar to that assigned by Nitzsch to Coracias and Eurystomus." These features are diagrammatically represented in a woodcut (fig. 5, I. c). The following is a more detailed description :- The inferior tract divides about 1 inch behind the junction of the rami of mandible-the (badly) so-called "chin-angle"-from which it starts as a narrow, single tract2. Between this tract and the mandibular rami, extending as far as the angle of the jaw, a narrow naked space is left; at this point the inferior tract becomes continuous with the feathering of the head above, so that here the neck, except for the narrow median ventral apterium, is continuously feathered. This continuous feathering extends downwards till about | inch above the shoulder, when, the inferior and dorsal tracts diverging, the lateral neck-space is formed. The inferior tracts diverge gradually as they approach the breast, and then run parallel to each other over the pectoral muscles and abdomen to the sides of the vent, leaving a rather wide bare carinal space, with a few scattered down-feathers. As the inferior tract emerges on the breast, it gives off a branch to the anterior margin of the patagium ; and this at first is dilated somewhat, so that the space between it and the main tract is feathered. The broad humeral tract is also connected with the inferior tract where the latter gives off this patagial branch. In the lower part of the neck the inferior tract is about 8 feathers broad, on the breast about 6, and on the abdomen only 2. About the middle of the sternum the outer pectoral tract, which is about 4 feathers wide and slightly stronger than the main tract, is given off; it is 1 This disposition of the fourth toe makes Leptosoma, at first sight, look as if it had three toes anteriorly directed, and no doubt accounts for Mr. Sharpe entirely omitting any notice of its peculiar feet in his paper on the Coraciidse (cf. Ibis, 1871, pp. 187, 285). 2 In Coracias garrula the naked median space left between the halves ol the inferior tract extends quite up to the symphysis, so that the inferior tract is double from the commencement. PROC. ZOOL. Soc-1880, No. XXXI. 31 |