430 ■ PERCY SLADEN TRUST EXPEDITION 



assuming that they will ever prove as interesting to the zoogeographer as land and fresh- 

 water mollusca have been. 



Whenever possible, attention has been paid to the anatomy of the forms included in 

 this collection, and several points of interest have been revealed. The author has been 

 struck, while in the course of this work, with the necessity for a more intensive study 

 of these animals for the purposes of systematic zoology. Any worker familiar with the 

 Cephalopod mandible and radula will recall how at first sight these structures differ to 

 a remarkably slight degree in forms placed very widely apart. It seems likely, however, 

 that closer study will reveal differences between the radulse of such forms. The author 

 has been impressed by the way in which, in apparently similar radulse of forms otherwise 

 very distinct, certain elusive and subtle differences may remain constant over a series of 

 examples. The shells of certain groups of land mollusca have been separated into a 

 number of species which, to the ordinary observer, exhibit very little difference one 

 from another. It is claimed by conchologists that the differences between them are 

 constant, however subtle and minute they may be. Very much the same sort of thing may 

 be found by intensive study among the Cephalopoda. 



Among the internal organs the author has found that the genitalia and heart are 

 frequently strongly characterised ; and it often seems that for a provisional arrangement 

 these organs would supply a more useful clue to identity than the radula and mandible. 

 On the other hand due care has to be exercised, especially with regard to the heart, that 

 characteristics such as are probably occasioned by the temporary physiological state of 

 such organs are not registered as of diagnostic value. 



The author is indebted to Dr W. E. Hoyle for information with regard to the 

 Cranchiidee, and to the Rev. Dr H. M. Gwatkin for the loan of a series of radula-prepara- 

 tions which has been of great value in determining the affinities of certain forms. 



The types and a series of other specimens have been presented by Prof. Gardiner to 

 the British Museum. 



The following arrangement has been adopted from Pelseneer (14), Pfeflfer (16), and 

 Chun (2). 



Class CEPHALOPODA. 

 Order 2. DIBRANCHIA. 

 Suborder 1. DECAPODA. 

 Tribe I. (EGOPSIDA. 

 QIgopsida libera. 



Family 2. Onychoteuthidae, 



Onychoteuthis, sp. (immature). 

 Teleoteuthis, sp. (immature). 



3. Enoploteuthidse. 



Ahralia (Compsoteuthis), sp. (immature). 

 ,, sp. (immature). 



