Miscellaneous. 71 



Nassa exilis, Powis. 



N. panameims, C. B. Ad. 



Nassa complanata, Powis. 



N. gemma^ Phil. 



N. cellaria, Brit. Mus. A small variety. 



Nassa concenti-ica, Marrat. 

 N. conci'nna, Reeve, sp. 82; not the concinnn, Powis, Reeve, sp. 91. 



Nassa gaudiosa, Hinds, is not the shell tigured in Reeve under that 

 name. 



Nassa Bronn'i, Phil., is a variety, with the outer lip muricated, of 



N, coronata, Lam. 



100 Edge Lane, Liverpool. 



Tlie Number of Classes of Vertebrates, and their Mutual Relations. 

 By Prof. Theodore Gill. 



The mind, untrained in scientific logic, in its generalizations re- 

 specting the animal kingdom, if we may judge by the vague ideas 

 elicited by inquiry and by the history of science, instinctively asso- 

 ciates its subjects into groups determined by the nature of their 

 habitat ; and hence we have had the vertebrates differentiated into 



(1) those especially adapted for progression on land (Quadrupeds), 



(2) those especially fitted for progression through the air (Birds), 

 and (3) those adapted for life in the water (Fishes) ; while the 

 residue, not readily combinable with either of those classes, are 

 tacitly overlooked, or, as the serpents, annexed as a kind of appendix 

 to the Quadrupeds, because they most resemble certain of those 

 animals — the lizards. It was therefore a great advance when 

 Linnaeus established a peculiar class (Mammalia) for the typical 

 viviparous quadrupeds and the whales, and thus for the first time 

 subordinated habitat and adaptation therefor to structure. ^Miile 

 at the present day the ancient ideas have almost entirely disappeared 

 from the system of nature so far as regards the terrestrial verte- 

 brates, they are still to a great extent prevalent in the appreciation 

 of the relations of the aquatic ones. Por those vertebrates con- 

 founded by most naturalists under the name of Fishes are very dis- 

 similar among themselves, and so much so even that the difterences 

 are more marked and radical than those between any of the superior 

 classes of the branch. If, indeed, considerations of differences of 

 structure are to guide us in the appreciation of the relations and sub- 

 ordination of animals, the current classification must be entirely 

 changed, and the subordination of the highest groups, first sug- 

 gested by Hiickel, should be adopted witli some modilications, while, 

 as respects the combination of the " higlier " or more specialized 

 classes into superior groups, other principles should guide. One of 

 the chief points to be reconsidered is the association of the Batra- 

 chians with Fishes rather than with the true reptiles. Although no 



