ON THE VERTEBRATE SKELETON. 181 



tend for the perpetual expression or insertion of the understood generic word 

 'bone' or 'os' in this case any more than in the parietal, frontal, &c, which, 

 from being originally specific adjectives, have been properly and conveni- 

 ently converted into definite nouns. 



In conformity with this mode of acquiring an improved as well as brief 

 and precise expression of anatomical facts, I have substituted for 'pars petrosa' 

 or 'os petrosum' the substantive term 'petrosal' (Lat. petrosum, figs. 5, 25, 16). 

 The necessity for some such designation for an essentially and often physically 

 distinct bone in the vertebrate skull has been felt by both Cuvier and 

 GeoffVoy, when they respectively proposed the names 'rocher' and ' rupeal' 

 for the element in question. ' Petrosal' has appeared to me to be the best 

 English equivalent of Cuvier's ' rocher' ; as containing the most character- 

 istic vocable of the old anthropotomical descriptive phrase ' pars petrosa 

 ossis temporis,' &c. ' Rupeal' unfortunately has no determinate meaning : it 

 is applied by its author with certain prefixes to several distinct bones, which 

 already had their proper names. ' Sclerotal' (sclerotale, Lat., figs. 5, 22, 23, 17) 

 for ' ossicula seu laminae osseae membranae sclerotica?,' is proposed on the same 

 grounds as exoccipital, postfrontal, &c, viz. the substitution of a name for a 

 phrase. The sclerotals have not been usually included amongst the bones of 

 the head, though they have precisely the same claims to that rank as the pe- 

 trosals, or other bony capsules of the organs of special sense. Retaining the 

 old anthropotomical term ' ethmoid,' I restrict its application to the very irre- 

 gular and inconstant developments of bone in the cartilage or membrane 

 which is applied to the anterior outlet of the cranium proper, for the support 

 or defence of the cranial part of the organ of smell. The ' ossa turbinata supe- 

 riora,' and the ' cellulas aethmoideae' are parts of the capsule of that sense, ex- 

 tensively developed in the mammalia, to which the term ethmoid may properly 

 apply ; but they must always be distinguished from the modified though con- 

 stant neurapophyses of the nasal vertebraj called ' prefrontals,' with which the 

 above developments of the olfactory capsule usually coalesce in birds and mam- 

 mals. 'Turbinal' (turbinate, ^at^fxgs. 5,25, 19), like petrosal, is a substitute for 

 the phrase 'os turbinatum inferius,' and its synonym 'os spongiosum inferius.' 



' Palatine' (palatinum, Lat., ib. 20) is another of the few fortunate instances 

 of the general recognition of the homologous bone throughout the vertebrate 

 kingdom, with the further advantage of a steady retention of a good old name. 



' Maxillary' (maxilla, Lat., ib. 21) is a similar instance ; but Geoffroy, as 

 usual, makes himself singular by adding an uncalled-for synonym. If 

 Soemmerring's term 'mandibula' for the lower jaw were universally adopted 

 and constantly understood to signify the totality of that part of the tympano- 

 mandibular arch throughout the vertebrate series, it would be unnecessary 

 to encumber ' maxilla' with the distinctive epithet ' superior,' which, indeed, 

 expresses a character peculiar only to Man and a few mammalia : in the ver- 

 tebrate series the 'maxilla' is more commonly anterior than superior to the 

 * mandibula.' 



I have adopted the term ' premaxillary' (premaxillare, Lat. ib. 22), as used 

 by M. de Blainville and some other distinguished continental osteologists, in 

 preference to ' intermaxillary ;' because that term has already been applied 

 (by Schneider) to another bone of the skull (the tympanic in birds), of which 

 it is more accurately descriptive, than it is of a bone which is more com- 

 monly before than between the maxillary bones. ' Entopterygoid' (entoptery- 

 yoideum, Lat.) claims preference to the phrases 'pterygoide interne' of Cuvier 

 and Agassiz, on the same logical grounds as have already been urged in favour 

 of ' exoccipital,' ' prefrontal,' &c. But I have also another reason for pro- 

 posing a definite term for the bone 23, fig. 5, which I regard as a peculiarly 



