LIGHT PRODUCTION IN CEPHALOPODS. 149 



gone into in any detail here. The attempt has been made to be 

 both conservative and judicial, but it of course goes without 

 saying that the result attained must be regarded as far from 

 final. Aside from matters of judgment even, it would be 

 presumptious to claim for this list either completeness or freedom 

 from error, but every effort has been made to reduce unneces- 

 sary mistakes to a minimum, and after all it is utility rather 

 than finality which must always be remembered as the end in 

 view. In certain special cases where the number of valid species 

 seems to be more than usually problematic, this circumstance 

 has been so indicated by the use of + or signs. 



TABLE I. 1 



SYNOPTIC TABLE OF THE CLASS CEPHALOPODA, SHOWING THE 

 OCCURRENCE OF PHOTOGENETIC ORGANS. 



Class CEPHALOPODA. 

 Order TETRABRANCHIATA. 



Suborder NAUTILOIDEA. 

 Family NaulilidcB. 



Genus Nautilus Linnaeus 1758. (No photogenic species known.) 



3 or 4 species. 



Order DIBRANCHIATA. 



Suborder DECAPODA. 



Division CEcopsiDA. 

 Superfamily Architeuthoidea. 



Family Architeuthid.ee. (No photogenic species known.) 

 Genus Architeuthus Steenstrup, 1857. 



14 species. 



Superfamily Enoploteuthoidea. 



Family Gonatids. (No photogenic species known.) 

 Genus Gonatus Gray, 1849. 



3 species. 

 Family ONYCHOTEUTHID.-E. 



Genus Onykia Lesueur, 1821. (No photogenic species known.) 



12 + species. 



Genus ONYCHOTEUTHIS Lichtenstein, 1818. (2 axial photogenic organs in 

 pallial chamber.) 



1 established species, banksii; several doubtful. 



Genus Tetronychoteuthis Pfeffer, 1900. (No photogenic species known.) 



2 species. 



Genus CHAUNOTEUTHIS Appellof, 1891. (Photogenic organs in ventral in- 

 tegument of mantle Chun; no luminous organs Pfeffer.) 

 i species: mollis. 



1 Photogenic families and genera are printed in small capitals. 



