PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 413 



tion from the teleosteoid to the most abnormal forms. Tlie group will 

 therefore stand, whatever may be the ultimate valuation of its charac- 

 ters by taxonomists. My conservative instincts impel me to retain the 

 group with its generally recognized ordinal valuation. It is, it is true, 

 of less taxonomic value than the Pediculates, the Apodes, or the Nema- 

 tognaths, and of very much less importance than such orders as the 

 Dipnoaus, Crossopterygians, and Chondrosteans ; but, on the other 

 hand, its characters are of greater significance than such as are used for 

 ordinal distinction in the class of birds, and therefore it may be well to 

 keep it in the system till our knowledge of the whole is more ripe. 



As to the affinities of the families, there is sufficient evidence to indi- 

 cate their genetic relations tolerably well, and we have a regular series 

 of gradations from the Triacanthidai diverging in different directions. 

 The ramifications of the group are indicated in the following tables, in 

 which the left fork in each case indicates the most generalized form, 

 and the right ones the successivelj^ more and more specialized forms. 



Teleocephali. 

 (Teuthydoidea.) 



( — 



-.A__ 



H td 





8 



p 



GO 





(Tt- 



p 

 o 



8 



o 

 o 



„/^~ 



r- 



O 



p- 

 o 



p- 



o 



P^ 



o 



a 



c-l- 



P' 



g ^ 



Pi 



p 

 o 

 p 



d 



I doubt not that objections will be made to an undue multiplication 

 of families. When a comparison is made with their characters and 

 those of generally accepted families in more familiar groups, their im- 

 X)ortance must be sooner or later acknowledged. It is to be hoped that 

 naturalists may make use of their reasoning powers in considering them, 

 and not assume that thej^ are unjustifiable because previous students 

 had not ai^preciated their value. 



In conclusion, I have to make especial acknowledgment to the various 

 memoirs on the Plectognaths i)ublished by Mr. Hollard. Had they not 

 been neglected or practically ignored by his successors, a consistent 

 system of the order would not have been deferred so long. The diag- 

 noses have been made as brief as was consistent with clearness ; the 

 characters given are reinforced by others often as important, although 

 not so patent as those used. 



