BATHTTOMA. 49 



states that they have not a twisted columella. As the possession 

 of this is a typical generic factor, it may be observed that the 

 French author's statement is not correct; and though, it is true, 

 the figures accompanying Professor Tate's memoir ^ do not exhibit 

 a twist or plication, that author expressly states- that the specimens 

 have a slightly twisted columella. 



Pleurotoma atradoides, Watson, dredged by the "Challenger" 

 off the Philippines in 375 fathoms of water, should be relegated 

 to this genus. 



Type. — Murex cata2)hr actus, Brocchi. 



Bathytoma angustifrons, Tate (sp.). 



1893. Dolichotoma angustifrons, Tate and Dennant, Trans. Eoy. Soc. 



South Aust. vol. xvii. pt. 1, p. 221 (Hst name). 

 189-1. Genotia angustifrons, Tate, Joum. Eoy. Soc. N.S.W. p. 175, pi. x. 



figs. 7, 7a-i {non 7c). 



Protoconch composed of two turns, somewhat oblique and 

 slightly longitudinally striated anteriorly. The elevation or 

 depression of these turns to a large extent determiues the 

 relative elongation in the growth of the whole shell. Where 

 it is depressed, the whorls tend to become broad and strongly 

 keeled; where, on the other hand, it is much elevated, the 

 carinations are not so sharp and the shell becomes very long. 

 It is interesting to observe also that but few of the main features 

 of the ornament were foreshadowed in the brcphic stage, and the 

 extremely diversified character of that ornament as the animal 

 became adult is mei'ely an individual characteristic, of no value 

 for systematic purposes. If the shells of a number of very young 

 specimens be compared, no one would have any difficulty in 

 relegating them to a single species; but as they get larger the 

 ornament tends to become so variable that many malacologists 

 would feel inclined to admit the extreme types of variation as 

 of specific rank. Professor Tate's description and figure refer 

 to a commonly prevailing form. 



The sinus in this species is unusually deep, though not more 

 so than in some forms of the type species from the Pliocene of 



• Journ. Roy. Soc. X.S.W. vol. xsvii. 1894, pi. x. fig. 7, etc. 

 ' Op. cit. p. 174. 



