JOURNAL OF CONCHOLOGY. II9 



BIBLIOGRAPHY. 



Mollusca of H.M.S. 'Challenger' Expedition.— 



By the Rev. Robert Boog Watson, B.A., F.L.S., &c., — Parts 

 4— II. 



The magnificent results of the cruise of the 'Challenger' in 

 the discovery of new forms and throwing light upon many aspects 

 of Conchology previously obscure, owe much of their value to 

 the untiring, able, and conscientious study bestowed upon them 

 by their talented Reporter. In part 5, Mr. Watson formulates 

 some conclusions he has arrived at from the investigations he is 

 engaged upon. 



I. — Depth is an important condition of Molluscan life, 

 there being really shallow and deep water species and 

 genera. 

 2. — Temperature seems to be even more important than 



depth. 

 3. — Great differences in depth and temperature are barriers 



to distribution. 

 4. — Living species found also fossil always have a wide 



local distribution. 

 5. — Where barriers of depth or temperature do not check 

 dispersal, there seems in ordinary circumstances no 

 limit to universality of distribution. 

 6. — There are existing species universally distributed, 



having overcome all obstacles of dispersion. 

 7.— The absence of any trace of lasting, essential, and 



progressive change. 

 The third part is commenced with Basilissa oxytropis from 

 Ascension Island omitted from its proper place. Trochid^ 

 follows with 1 6 species, one being referred to Gibbula — glyptus 

 from Sydney. Ziziphinus has three species — Z. stirophorus 

 from Culebra ; Z. tiara from Culebra and the Bermudas ; Z. 

 transenna from Philippines ; Margarita has twelve species, 

 viz : — T. brychius from Kerguelen ; T. charopus from Kerguelen 

 Islands ; and var. cceruleus from Heard Islands ; T. pompholu- 



