No. 2.] AM/A AND TELEOSTS. 85 



It is thus evident, in so far at least as the ganoids and tele- 

 osts are concerned, that the most anterior spino-occipital nerve 

 of Furbringer's nomenclature must lie, morphologically, between 

 the protometameric part of the cranium and the first posterior 

 assimilated, or partly assimilated, vertebra. The most posterior 

 spino-occipital nerve, where there are more than one, should 

 then lie, necessarily, between the last and the next to the last 

 assimilated vertebrae, and the first free spinal nerve between 

 the last assimilated vertebra and the first free one. These 

 necessary relations of the last-named nerves to the skull and 

 vertebrae, thus definitely indicated by inference, seem not to 

 have been carefully borne in mind by Fiirbringer in his general 

 definitions and conclusions, although it is sufficiently evident that 

 they are of primary importance in any attempt at comparison. 



In Amia calva, Fiirbringer found, as I had found independ- 

 ently of him (No. i), four nerves between the vagus and the 

 first free spinal nerve. The most anterior of these four nerves 

 is said by him to belong to the occipital nerves of his nomen- 

 clature, the other three to the spino-occipital ones. The occip- 

 ital nerve is designated by the letter z, the other three by the 

 letters a, b, and c. The nerve next posterior to the nerve c is 

 said to be the first free spinal one, and is designated by the 

 number 4. In other fishes, in which there may be other occipital 

 or spino-occipital nerves, not found in Amia, the additional 

 occipital ones are said to always lie anterior to the one occipital 

 nerve of Amia, and the additional spino-occipital ones always 

 posterior to the three spino-occipital ones of that fish. 



In teleosts, Fiirbringer finds but two spino-occipital nerves, 

 and he considers them as the homologues of the nerves b and 

 c of Amia. On page 465 of his memoir he says, that the 

 occipital nerves are wholly wanting in all teleosts, and that the 

 existence of the first spino-occipital one has not yet been estab- 

 lished in any teleost known to him. On page 543 he further 

 says, that in teleosts, not only all the occipital nerves but also 

 the first spino-occipital nerve is "vollstandig riickgebildet." 

 The nerve next following the nerve c is said to always be, as in 

 Amia, a free spinal one, and it is accordingly designated, as in 

 that fish, by the number 4. 



