OCR Text |
Show 1893.] OSTEOLOGY ETC. OF THE DINORNITHIDiE. 171 examination of numerous immature specimens the ossification has been determined, and outline figures are given showing the boundaries of all the bones and their share in the various ridges, processes & c , the special characters of which are of classificatory importance. Next follows a detailed comparison of the skulls of the Moas with those of the other Ratita?, this section ending with a summary of cranial characters in the whole subclass. A table of measurements is then given showing the chief dimensions, in millimetres, of the skull in the more important species of Dinornithiclas and in the other genera of Ratita?. Care is taken to define as exactly as possible the precise way in which the measurements are made. A second table gives the leading measurements expressed as percentages of the length of the basis cranii, a series of indices being thus obtained which are frequently of use in the definition of genera and species. The author next discusses the bearing of these facts upon the question of the division of the Dinornithidos into genera. H e finds that-judging from the skull alone and taking no cognizance of the rest of the skeleton-five genera can be distinguished, viz. Dinomis, Pachyornis, Mesopteryx, Anomalopteryx, and Emeusx. Moreover, Pachyornis, Mesopteryx, and Anomalopteryx are found to present many points of resemblance with one another, of which the most obvious is the narrow7, pointed beak. The two broad-beaked genera Dinomis and Emeus, on the other hand, differ strikingly both from one another and from the narrow-beaked forms. Relying on cranial characters only, the Dinornithidce may therefore be divided into three subfamilies as follows : - Subfamily a. DINORNITHIN^E. Genus Dinomis. Subfamily b. ANOMALOPTERYGIN.E. Genera Pachyornis, Mesopteryx, and Anomalopteryx. Subfamily c. EMEIN^E. Genus Emeus. This section of the paper ends with a summary of the cranial characters of the subfamilies and genera. Lastly, the phylogeny of the group is discussed. Mesopteryx is considered to be the most generalized form, while Dinomis and Emeus are both highly specialized but in opposite directions. Of the other Ratita?, Apteryx comes nearest to the Moas in the structure of its skull, and strong affinities are shown by both Casuarius and Dromceus to the N e w Zealand genera. Struthio and Rhea, on the other hand, show no special affinities, as far as the skull is concerned, either to the Australian forms or to one another. 1 No account is taken of Megaloptcryx, which is included by Lydekker among the Binornithida, as nothing is at present known of its skull. |