CLASSIFICATIOK, AND PHTLOGENY OF THE DINOENITHID^. 405 



facets are so close together that the head is virtually single. In Dromceus alone 

 there is a facet on the base of the otic process, just anterior to the lateral ridge, 

 for articulation with the surface ah-eady mentioned on the zygomatic process. 



It was pointed out that in all the Moas there is a pneumatic foramen on the mesial 

 surface of the otic process, while a second foramen occurs on the posterior surface in 

 certain instances. The only other case in which I have found the mesial foramen is 

 that of Struthio, in which there is an extremely small aperture in the corresponding 

 position, looking, however, more like a vascular or nervous than a pneumatic foramen. 

 The posterior foramen is of moderate size in the Emu and Cassowary, and is situated 

 near the base of the otic process ; in the Ostrich it is higher up and proportionally 

 smaller ; in Rhea it is on the posterior margin of the head, immediately below the 

 articular surface. In the adult Kiwi there are several small foramina in the same 

 position, but at the time of hatching there is a single large foramen in the same position 

 as in Anomaloj)teryx. The otic process in Apteryx is peculiar for sending off small 

 mesial and lateral processes just below the head. 



In the orbital process the Cassowary presents the closest resemblance to the Moas, 

 but is more compressed and blunter at the apex than in the latter. In the Emu it is 

 blunt and thick, and takes a more nearly horizontal direction than usual. In the Ostrich 

 it is also compressed and the apex truncated. In Bhea it is extremely short and blunt. 

 In Apteryx it is unusually long and strongly compressed, so as to have the form of a 

 thin vertical plate with a thickened ventral rim. 



In the mandible the internal angular process and ridge are best developed in Apteryx 

 and to a less degree in Rhea, but are also well marked in Dromceus and Casuarius. 

 The posterior angular process and ridge are large in the Ostrich, Emu, and Cassowary, 

 obscure in the Rhea and Kiwi. In the general form of the jaw the Moas come nearest 

 to the Cassowary, in which the rami are moderately stout and slightly deflected distally. 

 The comparative weakness of the mandible in the other large Ratitse is very marked, 

 and in Apteryx the immense length of the symphysis separates it at once from all 

 the other genera ; in the strength and solidity of the jaw and in the size of the 

 coronoid process Apteryx australis is, however, the only form which approaches the 

 DinornithidsB. 



5, Measurements of the Skulls op the Ratit^. 



Measurements of the skulls of Moas are given by Owen, Haast (5), and Button (9). 

 It is, however, desirable for purposes of comparison that a more complete set of 

 measurements should be given, and that the precise way in which they are taken should 

 be accurately defined. 



Owing to the early ankylosis of the bones of the cranium, it is impossible to determine 

 VOL. xiiT. — PART XI. No. 5. — Octoher, 1895. 3 M 



