4 04 SCIENCE PROGRESS. 



sesses a double head for articulation with the skull, changed 

 his opinion, and now considers them as degenerate Carinatse 

 in which the wing has been reduced in size. 



Till recently our knowledge of the Stereornithes depended 

 almost entirely on the preliminary notices of Ameghino, 

 and on the plates of the catalogue of Moreno and Merce- 

 rat. At the beginning of last year however the former 

 author published by far the most important contribution 

 (12) to this subject that has yet appeared. He now de- 

 scribed not only the specimens to which his preliminary 

 notices referred, but also a large number of additional 

 remains. The classification followed in this paper is dif- 

 ferent from that in his " Enumeracion," the order Stereor- 

 nithes being adopted and subdivided into two families, the 

 Phororhacidcz and Opisthodactylidce. In the former Pele- 

 cyornis and Lophior'nis are now included, while Anissolornis 

 is considered to be a Gallinaceous bird : several new genera, 

 some of which appear to be of rather doubtful validity, 

 are also added. The Opisthodactylidce include one genus 

 only, Opisthodactyhis. 



Of the Phororhacidcz the skeleton of Pkororkacos injlatus 

 is by far the most completely known, the skull, mandible, 

 pelvis, the bones of the fore and hind limb, and some 

 vertebrae being described and figured. The skull is of 

 a very remarkable appearance ; from the side it most 

 resembles that of a Raptorial bird, the enormous beak 

 being sharply hooked at the anterior extremity, but when 

 looked at from above it is seen to be much compressed, 

 so that the premaxillary region, though very deep from 

 above downwards, is extremely narrow from side to side. 

 The quadrate has a double head for articulation with the 

 skull, a character which, as Lydekker has pointed out (13), 

 is opposed to the inclusion of these birds in the Ratitce. 

 The mandible is very heavily built, and its anterior end is 

 curved upwards in a manner very unlike the ordinary avian 

 mandible. The sternum is, unfortunately, quite unknown, 

 but the coracoid and scapula have been preserved. The 

 former is long and slender, quite unlike that of any Ratite 

 bird ; the acro-coracoid process is almost entirely wanting, and 



