176 Dr. T. Gill on the Homologies 



Therefore those elements cannot be carpal, but must repre- 

 sent the humerus. 



II. The element with which the homologue of the humerus, 

 in Polypterids, is articulated must be homologous with the 

 analogous element in Dipnoans, and therefore with the 

 coracoid. 



The coracoid of Polypterids is also evidently homologous 

 with the con-esponding element in the other Ganoids ; and 

 consequently the latter must be also coracoid. 



It is equally evident, after a detailed comparison, that the 

 single coracoid element of the Ganoids represents the three 

 elements developed in the generalized Teleosts (Cyprinids &c.) 

 in connexion with the basis of the pectoral fin ; and such 

 being the case, the nomenclature should correspond. There- 

 fore the upper element may be named hypercoracoid, the 

 lower hypocoracoid^ and the transverse or median mesoco- 

 racoid. 



III., IV. {Proscapula^ or united scajmla and ectocoracoid.) 

 The two elements of the arch named by Parker, in Lepido- 

 sirenj " supraclavicle " (= scapula) and " clavicle " (= ecto- 

 coracoid) seem to be comparable together and as a whole with 

 the single element carrying the humerus and pectoral fin in 

 the Crossopterygians [Polypterus and C alamo ichthys) and 

 other fishes*, and therefore not identical respectively with 

 the " supraclavicle" and " clavicle" (except in part) recognized 

 by him in other fishes. 



As this compound bone, composed of the scapula and ecto- 

 coracoid fused together, has received no name which is not 

 ambiguous or deceptive in its homological allusions, it may be 

 designated the proscapula. 



V. The posttemporal of the Dipnoans is evidently repre- 

 sented by the analogous element in the Ganoids generally, as 

 well as in the typical fishes. 



The succeeding elements (outside those already alluded to) 

 appear from their relations to be developed from or in connexion 

 with the posttemporal, and not from the true scapular appa- 

 ratus ; they may therefore be nsimo,^ posttemporal^ posterotem- 

 poralj and teleotemporals. 



The homologies of the elements of the girdle of Dipnoans 

 with those of other fishes, and the added elements in the latter, 

 will be as follows : — 



* Dr.Giinther (Phil. Trans, vol. clxi. p. 631) has observed, respecting the 

 division in question in Lepidosiren and Ceratodus : — " I cannot attach much 

 value to this division ; the upper piece is certainly not homologous with 

 the scapula of Teleosteau fishes, which is far removed from the region of 

 the pectoral condj'le." 



