66 PHYLOGENY OF FUSUS AND ITS ALLIES. 



A little later the upper of the two spirals becomes stronger, thus pro- 

 ducing a unicarinate aspect. The ribs are at first strong and the 

 spirals sharp and prominent, and between them, in the fifth or sixth 

 volution, simple rounded secondary spirals appear by intercalation. 

 The whorls gradually become bulging in the center and the ribs obsolete 

 toward the sutures, but prominent in the middle. The simple inter- 

 calation continues for some time, after which from one to three addi- 

 tional ones appear on each side of the secondary spiral. The ribs gen- 

 erally become obsolete on the last whorl of the adult, and a not very 

 prominent keel — the stronger central spiral — remains. In some cases 

 the ribs are lost on the young specimen, showing individual acceleration. 



In the younger specimens the spindle and anterior canal are pro- 

 portionally longer than the spire, while in mature shells they are pro- 

 portionally shorter. The striking feature of this shell is the vertically 

 compressed character of the whorls which shortens and thickens it, 

 giving it an appearance similar to that of F. distans. 



In some adult specimens the prominence of the keel decreases, until 

 the whorls appear round. In fact I am convinced that in a sufficiently 

 large collection all the structural variations found in the colus series, 

 will be represented. Parallelism appears to be the rule in the develop- 

 ment of the species of Fnsus, and it is to be seen in nearly every genetic 

 series within the genus. The shells of the present species are covered 

 with an olive brown periostracum. 



A specimen in the Philadelphia Academy of Science collection has 

 the characters and outline of this species with a bicarinate young, but 

 it has its spirals noduled in a striking manner, which is wholly unlike 

 that of normal specimens of the species. 



The radula of this species is much like that of F. inconstance 

 Lischke, the central teeth being slightly different. 



Localities: South Australia (M. C. Z. , Nat. Mus. 91749, 



16635) ; Indo-Pacific (M. C. Z. 34, Acad. Sci.). 



FUSUS BRASILIENSIS sp. nov. 



(Plate IV, figs. I to 4.) (Type fig. 2.) 



The protoconch of this species is somewhat less oblique than the 

 normal, appearing slightly more depressed from above. It consists 

 of one and one half volutions, the last portion of which are furnished 

 with vertical riblets, which toward the end become strong. The whole 

 aspect of the protoconch recalls that of the Italian Tertiary Fusi. 



The conch begins with rounded whorls, which at first are less 

 bulging in the middle than those of the preceding species. The shell 

 thus appears more cylindrical in the young. There are two strong 

 central spirals visible, giving the appearance of bicarination. There 

 are really three of these strong peripheral spirals, the lower one, how- 



