132 



PHYLOGENY OF FUSUS AND ITS ALLIES. 



Fig. 1 8. Clavilithes 

 chamberlaini type. 

 (After Johnson and 

 Grabau.) 



CLAVILITHES CHAMBERLAINI Johnson and Grabau. 



1901. Clavilithes chamberlaini Johnson and Grabau, Proc. Acad. Nat. Sci. Phil., 

 Nov., 1901, p. 602, figures in text. 



This species is the structural equivalent of 

 the Parisian C. scalaris and the British C. 

 longcuvns. 



The spire of this species is long and slender, 

 as in C. kenncdyanus Harris, with which the 

 early whorls of the shell agree pretty well. Only 

 a portion of the protoconch has been observed, 

 but it is apparently of the same character as that 

 of the American species of this genus generally, 

 unless more slender than the normal. The spire 

 contains about seven ribbed whorls ; the suture 

 is moderately depressed ; the ribs are swollen 

 near the middle, but become obsolete toward the 

 suture ; they are at first more than their width 

 apart, but later become broader and the inter- 

 spaces correspondingly narrower. A subsutural 

 band occurs, and is quite strongly marked on the 

 later ribbed whorls, indicating a pronounced posterior canal at this stage. 



Spirals on the first five whorls, single, coarser in 

 the center, but becoming finer toward the sutures ; 

 interspiral spaces broader than the spirals. Inter- 

 calation of secondary spirals begins on the sixth whorl. 

 On the seventh whorl the ribs become broad and ill 

 defined, tending toward obsolescence. Before they 

 have quite disappeared, a sutural shelf sloping some- 

 what outward and bordered by a slightly outward 

 projecting margin appears ; this very soon develops 

 into a serrated flange. At the same time the whorls 

 become almost smooth, the spirals usually only oc- 

 curring on the narrowed anterior portion or canal of 

 the body whorl. Length of the adult specimen figured 

 39 mm., diameter 18 mm. 



Compared with C. humcrosns var. tcxaniis Harris 

 it has more ribs on the spire, and these are more regular 

 and bulging, stronger spirals, and the well-marked 

 serrated flange. It also differs somewhat in outline, 

 the last whorl being broader than the corresponding 

 whorl of texanus. It differs from its European 

 parallels in many characters, chief of which are the 

 protoconch, the long ribbed spire, the character of the 

 sutural shelf and flange, and other points readily seen 

 on comparison. 



Fig. 19. Cla- 

 vilithes sp. An 

 immature indi- 

 vidual in the 

 rugosus stage. 

 It probably be- 

 longs to a spe- 

 c i e s which 

 never passes far 

 beyond this 

 stage, and thus 

 is ancestral to 

 both kennedy- 

 anus and cham- 

 berlaini. 



