376 Prof. J. F. Blake on 



Tegmina and wings pale hyaline, the venation olivaceous 

 or fuscous. 



The rostrum does not extend beyond the intermediate coxse 

 and the face is laterally coarsely striated. 



Long. excl. tegm., ? 12 millim., exp. tegra. 37 millim. 



Hah. Cashmere Valley, 6300 feet {Leech). Coll. Dist. 



LI. — RemavTcs on Shell-growth in Cephalopoda. 

 By Prof. J. F. Blake, M.A., F.G.S. 



The structure of the " shell " of a Sepia is so unlike that of 

 the Nautilus that any serious attempt to work out their homo- 

 logies must be heartily welcomed by all who are interested in 

 Cephalopoda. The Sepia is much the harder of the two to 

 understand, and well deserves the study that has recently 

 been bestowed upon it by E,iefstahl * and Bather f. Unfor- 

 tunately these descriptions of the soft parts within it do not 

 agree, though the difference is not on a point of very great 

 importance. 



It does not appear, however, that these studies throw much 

 light on the question from a geological point of view. That 

 is to say, we get no nearer understanding how a Nautilus- or 

 Ammonite- or Belemnite-shell is actually formed. When I 

 was writing the Introduction to my '• British Fossil Cephalo- 

 poda,' some six years ago, I examined the structure of the 

 Sepia with a view to obtaining light from it, and got as far 

 as the above-named writers have in the knowledge of the 

 hard ])arts, yet found no means of homologizing them with 

 those of a Nautilus or Belemnite with any approach to con- 

 viction. Nor do I find that these writers have anything 

 definite to add, but help themselves along by theory, even 

 without testing it by available facts. I wish to deprecate 

 this method in the interests both of the subject and the 

 workers. In the first place, it is not inductive science ; and 

 in the second the author of a supposed genealogy will find it 

 very awkward when further knowledge — and that not hard 

 to acquire — shows the facts to be dead against him. But 

 most of all it is to be deprecated for the damage it does to the 

 credibility of what are meant to be stated as facts by such 

 writers, as we never can tell whether what they say is fiom 

 autopsy or from mental conception. 



* Palasoutograpliica, Bd. xxxii. 1886. 



t ' Annals,' April 1888, p. 298. See also Geol. Mag. 1887, p. 446. 



