280 



may be remarked that in Branchiosaurus the so-called maxillary bone 

 is furnished, according to Fritsch (No. 14), with two or three irre- 

 gular lines of teeth lying internal to the main line, which certainly 

 seems to be a characteristic of a piscine dermopalatine bone, rather 

 than that of a piscine maxillary one. 



Furthermore, the so-called tentacle of the Gymnophionae, which 

 is supplied with a retractor muscle and is innervated by the superior 

 maxillary branch of the trigeminus, has, or may have, according to 

 WiEDERSHEiM (No. 46), at the point where the retractor muscle is 

 inserted, a small projecting papilla. There is thus, in the tentacle of 

 these amphibians, much that corresponds to, if it does not even suggest, 

 the maxillary folds or maxillary tentacles of Polypterus, Amia and 

 Siluroids ; and if there is here a close, or even an approximate, homo- 

 logy it is evident that the palatal plate and the tooth - bearing part 

 of the so-called maxillary of the Gymnophionae are the homologues of 

 the corresponding parts of the so-called maxillary of Polypterus, that 

 is of the dermopalatine of Teleosts. Of this homology I myself feel 

 fairly well convinced, but I can find nothing that warrants an opinion 

 as to whether the piscine maxillary bone is wholly wanting in the 

 Gymnophionae, or is fused with the dermopalatine and certain other 

 bones to form the so-called maxillary of the animal. This question 

 I hopi' to solve in the investigation I have just begun of Conger, for 

 the so-called maxillary bone of Conger, which quite certainly contains 

 the dermopalatine element of the skull of the fish, is traversed by a 

 canal that strongly recalls the "maxillary cavity" of the maxillary bone 

 of the Gymnophionae. If this so-called maxillary bone of this fish is 

 found to contain a piscine maxillary component, it would seem as if 

 the same component must also be represented in the maxillary of the 

 Gymnophionae. In this connection it is perhaps not unimportant to 

 note that Wiedeksheim describes no septom axillary bone in the Gymno- 

 phionae. 



As to the breathing -valve bones, the mandibular ones, or pre- 

 splenials, seem certainly represented in the presplenial bones of Baur's 

 descriptions of certain reptiles (No. 6), and this would seem an in- 

 dication that the maxillary ones might also be found in higher verte- 

 brates. These maxillary breathing- valve bones, are, however, not easily 

 traced, and I have the greatest hesitation in even suggesting what 

 their homologues may possibly be, for the whole history of the de- 

 velopment of the internal nares and the formation of a secondary 

 palate is here involved. 



The olfactory pit of fishes is, as is well known, enclosed in ex- 



