THE SHOULDER-GIRDLE IN FISHES. 19 



with ganoid roof-bones to the skull there is evidently only one category of bones to be seen from 

 the outside. In the ordinary Teleostei this is quite otherwise, for in these Fishes eciosteal bones 

 of the endo-skeleton crop up and appear amongst the subcutaneous splints. Thus, in the 

 common Cod-fish (Gadtis morrhud] every one knows that the endo-skeletal "ethmoid," "prse- 

 frontals," " post-frontals," " pterotics," " epiotics," and " supra-occipital," come up to the 

 inner face of the skin, and articulate with the subcutaneous "nasals," "lachrymals," "frontals," 

 " parietals," and " snpra-temporals." In the Trunk-fish (Ostraciori) this is not the case; but 

 a complete helmet of hexagonal ganoid bones overlies the feeble eciosteal bones of the endo- 

 skeleton, and the generally feeble, subcutaneous (parosteal) plates that belong to the exo- 

 skeleton. 



Now, these latter may be separate in the Polypterus; I believe they are not ; but if they are, still 

 the bones labelled So., Ep., Pr.f., and Elk., in the figures given by Professor Huxley, and just 

 referred to (op. cit., p. 22, figs. 16 and 17), are not the supra-occipital, epiotic, prae-frontal, and 

 ethmoid, but merely dermal bones overlying those regions, and which in different types may or 

 may not have endo-skeletal bones beneath them. As for the dermal bones, such as the 

 frontals and parietals, they may be separate from the outer ganoid plates, as in Ostracion; 

 or connate with them, as in the Sturgeon. All these things must be considered before the 

 cranial helmets, and the overlying bones of the Shoulder-girdle in the extinct Ganoids can 

 be understood. 



The reader may make himself certain that all the bones which can be seen from the surface 

 on these Ganoids are dermal, and it is also probable that the Shoulder-girdle and Skull were very 

 often not ossified at all; in many cases not more than is to be seen in the Trunk-fish (Ostraciori), 

 and in the Lump-fish (Cyclopterus) ; very seldom would the endo-skeleton come up to the hardness 

 seen in the recent Polypterus. Holding these things in memory, we will refer to fig. 2, p. 2, of 

 Professor Huxley's Memoir, which shows in a diagrammatic form the ganoid plates that cover 

 the skull, face, and shoulder of Glyptoltsmws. 



The plate marked Eth. is a ganoid scale covering the endo-skeletal "ethmoid;" those 

 marked Pr.f. and Pt.f. likewise cover the prse-frontal and post-frontal regions ; but do not answer 

 to those bones in the Teleostei. Both Pt.f. and Pt, o. belong to the same category, and arise 

 from the bifurcation of the supra-temporal series; for the "lateral-line" series, even in the 

 Teleostei, forks over the temples, to surround the eye ; the super-orbitals going over the orbit, 

 the sub-orbitals below, whilst the pras-orbital (or lachrymal) closes in the series in front. (See on 

 this subject my paper on the " Osteology of the Gallinaceous Birds and Tinamous," 'Trans. Zool. 

 Soc.,' 1863, vol. v, p. 212 ; and another on the " Ostrich's Skull," 'Phil. Trans./ 1866, vol. clvi, 

 part 1, pp. 177, 178.) The bone marked Sq. is not the "squamosal " (see my views in a note 

 to Prof. Huxley's ' Elem. Comp. Anat.,' p. 188), but the second supra-temporal; the bone 

 marked Ep. is the first (hindermost) of this series, and overlies the true epiotic bone or cartilage. 

 The next behind Ep. is the so-called supra-scapula, my " post-temporal " ; and the bones behind 

 that belong to the second thoracic-dermal cincture, some part of which is almost constantly seen 

 in the Teleostei as the post-clavicular series. S. o. is the single ganoid counterpart of the supra- 

 occipital splint ; I have it in the skull of a species of Anolis from Barbadoes, and it is constant, 

 but symmetrical in the Mammalia, lying above the true supra-occipital; but of course it only re- 

 appears as a subcutaneous bone in them. Pa., Fr., and Op. are rightly labelled, as these do truly 

 represent the parietals, frontals, and operculum. Professor Huxley is right (p. 40) in doubting 



