15 



hearing consisting only of the acoustic labyrinth excavated in cartilage 

 and provided with large otolithes, and, lastly, the blind nasal sacs, form 

 a cumulative body of evidence in proof that the Lepidosiren is a fish, 

 which far outweighs the argument to the contrary, founded on the reptile- 

 like development of its air-bladder and its conversion into an organ of 

 aerial respiration." 



After this able and elaborate summary, it will be only necessary to 

 notice some of the objections that have been since brought against the 

 reference of the Lepidosirenoids to the class of Fishes. The most 

 prominent of those objectors are Bischoff and Milne Edwards. The 

 former, influenced especially by the consideration of the position of the 

 posterior nostrils, believed that they were true Amphibians. He found 

 that the hinder nostrils opened into the cavity of the mouth near to the 

 commissure of the lips. Milne-Edwards himself admits that their abnormal 

 position may be in part accounted for by the absence of superior maxillary 

 bones. Nor is such a termination of the olfactory canal peculiar to the 

 Lepidosirenoids. An analogous arrangement occurs in the whole family 

 of Ophisuroids of Kaup, which has, consequently, been placed by that 

 naturalist in a peculiar section, called by him " Cryptomycteres" Those 

 apodal fishes " have a posterior nostril, which is placed in a cleft on the 

 border of the lip, or perforates the inner soft part thereof." The slight 

 resemblo.nce or analogy to that family in its elongated form, and the 

 character of the vertical fins, may be also remarked. It is further worthy 

 of note that in the Ophisuroids, as members of the order of Apodes, the 

 supramaxillary, as well as the intermaxillary bones are small. But in 

 the other families of Apodes, the nostrils preserve nearly their usual 

 ichthyic position and relation to each other. 



Milne-Edwards again urges as a previously neglected argument in favor 

 of the Amphibian nature of Lepidosiren, the opening of the ductus 

 pneumaticus of the pulmonary sacs into the ventral face of the digestive 

 canal. But we also find a similar arrangement in the species of the 

 genus Polypterus, animals whose piscine characters and affinities have 

 never been called in question. 



Milne-Edwards commences with the observation that the lungs of the 

 Mammals, Birds and Reptiles, as every one knows, always originate from 

 the ventral face of the digestive tube, whatever their position may be in 

 the splanchnic cavity, and it is only on the ventral side of the pharynx 

 that the opening of the glottis is found. He continues and remarks that 

 " it is the same with the Lepidosiren ; and if the resemblance between the 

 lungs of all these animals and the air-bladder of the Lepisostei and of 

 the Amice, was as great as Mr. Owen seems to think it is, we ought to find 

 this same character of organic relationship between the oesophagus and 

 the bladder of these fish. Now, it is quite the contrary ; for the kind of 

 pseudo-glottis which establishes the communication between this cellular 

 pouch and the digestive tube, originates from the dorsal face of the 



