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ERIK A : SON STENSIO 
In the first place with regard to the mandible the agreement between the Coelacanthids 
and the Dipnoans is not as great as was originally thought probable, but is limited al¬ 
most to the general shape. The bones described in the mandible of the Dipnoi certainly 
show at first sight fairly similar conditions to certain bones in the Coelacanthids, but a 
closer examination shows immediately that they are fewer and have probably been formed 
by fusion of other elements than in Coelacanthids. Besides as a matter of fact the bones 
in question show rather different conditions in different Dipnoi, e.g. in Dipterus and Ceratodus. 
In Dipterus the bone called «angular» by Traquair (1878, p. 7, PI. Ill) has probably 
its nearest equivalent in the supraangulo-angular of the Coelacanthids, while his «dental» 
certainly also includes the homologues of the splenial of the Coelacanthids (the most 
anterior or some of the most anterior infradental elements of the Rhipidistia), a fact 
which is clearly shown by the course of the mandibular canal. Conditions different from 
those in Coelacanthids are found also in the bones of the coronoid series, which, as we 
know, is represented both in Dipterus and other Dipnoans by a single large bone, 
usually called the «splenial». In addition Traquair describes, an articular in Dipterus. 
In the recent Ceratodus (cf. Gunther, 1871, pp. 521—526; Huxley, 1876, pp. 33 —34; 
van Wijhe, 1882, pp. 295—297, PI. XVI, fig. 14; Teller, 1891, pp. 18, 22, PI. Ill) the 
«angular» of Huxley’s description in 1876 may possibly include both the homologue of 
the dental and supraangulo-angular of the Coelacanthids, while the «dental» of the same 
description seems in fact to represent one or more of the most anterior infradentals of the 
Rhipidistids. Thus the latter bone may in my terminology used here be provisionally 
called the splenial. I ) It seems as if the reduction both in the hyoid arch and opercular 
apparatus has taken place independently in Coelacanthids and Dipnoans, as the primitive 
Rhipidistia generally may have been normally developed in this respect. 
In a number of Rhipidistids too the axial skeleton was developed in somewhat 
the same way as in Dipnoans and Coelacanthids, which in this case thus do not occupy 
any special separate position. As is shown by the investigations of Schmalhaussen (1913 a) 
summarized above, the diphyceral caudal fin of the Coelacanthids is probably developed 
secondarily from a Rhipidistid fin of the type found in Eusthenopteron and thus need 
not imply any direct relationship with the Dipnoans. 
Finaly it ought also to be mentioned that in the Coelacanthids an internal nasal 
aperture situated similarly to that of the Dipnoi is quite absent, while on the other hand 
such an aperture is found in the Rhipidistids (Stensio, 1918 c, p. 120; Dollo, 1895, 
p. 109; Watson and Day, 1916, p. 24), e. g. Dictyonosteus , Osteolepis, Diplopterus, Rhizodopsis 
and Megaliclithys. The nasal apertures of the Coelacanthids show instead almost the 
same conditions as those of the Actinopterygians, a fact that thus does not seem to 
support the view that their air bladder had a respiratory function. 
The facts mentioned here and what has been said of the caudal fin above (p. i 3 i) 
ought to show sufficiently clearly that characters indicating a very close affinity between 
Coelacanthids and Dipnoans really do not exist. Several of the resemblances between 
them are, as can clearly be seen, parallelisms. 
l ) As will, be seen from the works cited above and from K. Furbringer’s exposition in 1904 (pp. 442—444), 
there has been much discussion in the litterature on the homologues of the membrane bones of the mandibula in 
Ceratodus. 
