212 Notes on Acanthodian Sharks 
Skull and Branchial Arches.—To discuss the complicated structure of 
the skull and branchial arches of Acanthodians is hardly the part of the 
present paper. I have had, however, thanks to the courtesy of Professor 
Jaekel, the privilege of examining the extraordinary and beautifully pre- 
pared series of the Permian species, A. bronmi, in the Berlin Museum. 
And I am able to confirm the essential details given for this species, 7. e., 
the subdivision of the pterygo-quadrate and meckelian cartilages, as 
shown in Jaekel’s Fig. 1, in Zeitschr. deutsch. geolog. Gesell., 99, or 
Reis’s Fig. 1, Schwalbe’s Morph. Arbeiten, Vol. VI.“ One certainly finds 
little reason to dissent from the interpretation of these elements in terms 
of the succeeding branchial arches, for, in view for example of the condi- 
tions in the young Chimaeroid, we have clearly the grounds for con- 
cluding that the mandibular arch of primitive elasmobranchs was prob- 
ably a structure segmented like a branchial arch. Thus, in Acanthodes 
bronmt (Fig. 12), the epibranchial element is represented in the 
mandibular arch by the element g, the pharyngo-branchial by pt, the 
cerato-branchial by m, the basi-branchial by m’, and the hypo-branchial 
by c. What the anterior element, a, represents is by no means as 
probable. I am not convinced that Jaekel’s conclusion is a just one in 
regarding this as the “primary maxilla,” nor indeed his transcendental 
views as to the homologies of such parts of the mandibular arch as an 
“infra dental,” or an “ articular,” in his endeavor to demonstrate homo- 
logies between subdivisions of the Acanthodian mandible and the dermal 
bones of the jaw of higher forms.’ As regards the dermal sub-meckelian 
element, m”, one can also hardly subscribe unreservedly to the view that 
it represents the definite splenial of higher forms, for there is the obvious 
possibility, in view always of the fact that there are here no other dermal 
bones associated with the mandibular arch, that this element may be 
sui generis, without, however, going to the extreme view of Reis that it 
functioned as an extra-mandibular spine, which churned up the bottom 
and aided in securing the hidden food of the fish. 
This view of Reis, it may be added parenthetically, is founded in part 
upon his assumption that this dermal sub-meckelian element bore a 
series of appendages somewhat as branchiostegal rays. I have, however, 
a suspicion—for a final judgment one should of course compare Reis’s 
material—that the present appendances belonged in reality to the under- 
lying hyoidean arch; they are beautifully shown, for example, in the 
*Cf. the present Fig. 12. 
5 SB. Gesell. naturforsch. Fr. Berlin, 1905, p. 134 et seq. 
