MOKPHOLOGY OF TELEUSTEAN HEAD SKELETON. 531 



summarised all that is known concerning its presence or 

 absence in fishes, and describes it in considerable detail for 

 Aniia. Throughout he refers to it as the septo-maxillary. 

 Thus it has come about that to a bone in fishes undoubtedly 

 endosteal, there has been applied a name given by Parker to 

 one whose precise nature in the frog he does not state, but 

 which he classes among the " true dermal bones " in Lacerta 

 (78, p, 601). The same bone is present in Sphenodon 

 (Howes and Swinuerton, 01, p. 56), and is there undoubtedly 

 a true dermal bone. 



A somewhat similar state of affairs exists for other bones. 

 In higher vertebrates the squamosal, post-frontal, and pre- 

 frontal are purely dermal bones; but the bones in the Teleos- 

 tean skull to which these naiues are frequently applied, viz. 

 pterotic, sphenotic, and parethmoid, are cartih\ge bones with 

 a possible dermal origin. That the original dermal elements 

 in the latter case are the homologues of the dermal elements 

 in the former is still an unsettled question ; but even supposing 

 them to bo homologous, it has still to be decided whether 

 the ossification in cartilage which has lost all sign of its dermal 

 origin should be regarded as the homologue o£ the purely 

 dermal ossification.^ For these reasons the latter terminology 

 has been adopted throughout this memoir. 



The particular bone we are now considering should, there- 

 fore, have given to it some name which involves no doubtful 

 homologues, but accurately expresses its topographical rela- 

 tions. Following the terminology which is applied to other 

 ossifications of the ethmoid cartilage, I would suggest the 

 name Pre-ethmoid for it, as expressive of its relation to the 

 pre-ethmoid cornu. 



' In cases where actual genetic relationsliip lias been established between 

 dermal and cartilage bones, e.g. squamosal of Amia and pterotic of Teleosts, 

 such relationship could easily be expressed, and at the same time distinction 

 be maintained, by a more extended use of the prefixes dermo- and chondro — 

 thus, dermo-pterolic, choudro-iiterotie,— the former being used for bones which 

 are quite free of the cartilage, and the latter for those which involve cartilage, 

 irrespective of the degree of ossiQcation of this, or of the releiition of dermal 

 characters (cp. Bridge, 77). 



