comments by d. m. s. wal-^on 979 



Appendix B. — Comments by D. M. S. Watson 

 nomenclature of skull elements of permian tetrapods 



Principles. — Whenever possible, a bone is to bear the name which it 

 has in the human skull under the B. IST. A. list. 



When a bone is not represented in the human skull, it is to be found in 

 the crocodile and there named either after Cuvier or Owen, one or other 

 of whose names will be in common use. When there is any doubt about 

 the identification of a reptilian bone, it should not be called by a mam- 

 malian name. The most ineradicable errors are those which depend on 

 the mixing of characters of two animals under one name, and to call tlic 

 bone in the side of the brain-case of a crocodile alisphenoid deludes the 

 unsophisticated student into believing that it is certainly homologous with 

 the mammalian bone of that name. The use of a new term can mislead 

 nobody. In other words, I object to Professor Williston's remark: ^^(I) 

 am therefore disposed to retain the name alisphenoid until such time as 

 it is certainly shown to be something else.'' Much prefer to substitute: 

 "I refuse to call it alisphenoid until it is definitely shown to be homolo- 

 gous with the mammalian bone of that name." 



Ethmoid. — Three bones are known which include ethmoid as part of 

 their title : 



1. The Mesethmoid. — This is a cartilage bone replacing the cartilag- 

 inous nasal septum in Mammalia. 



2. The Ethmoturbinate. — A cartilage bone replacing the cartilaginous 

 scrolls developed from the middle of the paries nasi in mammals. 



3. The Sphenethmoid (W. K. Parker). — A cartilaginous ossification 

 in the front half of the orbitotemporal region and the posterior parts of 

 the planum antorbitale, septum, tectum, and solum nasi — only in frogs 

 and toads. The "ethmoid" of Caecilia is a general ossification of thi 

 whole anterior part of the cartilaginous skull, with many extensions into 

 membrane. 



From this it will appear that any bone which is to be called ethmoid 

 (either plain or modified) must be a cartilage bone in the anterior part 

 of the skull. 



The Interfrontal and Internasal, terms of my invention, are dermal 

 elements occni-ring not only in Stegocephalia, but in Osteolepis and 

 Dipterus. Any section across the top of the head of Eryops will show 

 that the interfrontal is quite distinct from the sphenethmoid, which lies 

 below it. 



The Internasal is equally a skin bone. They are to be distinguished 

 from the similar-looking bones on the top of the head of some frogs and 



LXXII— Bull. Geol. Soc. Am.. Vol. 28, 1916 



