PHYLOGENY OF FUSUS AND ITS ALLIES. I29 



compressed as is the case with the species of the British series, thus 

 producing a trochus-shaped apex. 



For the present I will leave these species under the generic designa- 

 tion of Clavilithcs, but with the understanding that they form a distinct 

 series, which may have originated independently. 



CLAVILITHES PACHYLEURUS (Conrad). 



1842. Fusus pachylenrns Conrad, Journ. Phil. Acad. Nat. Sci., vol. 8, p. 190. 



1848. Fusus pachyleurus Conrad, ibid., 2d ser-, vol. I, pi. 14, fig. 25. 



1865. Clavella pachyleurus Conrad, Am. Journ. Conch., vol. I, p. 18. 



1890. Fusus (Clavella) conjunctus var. pachyleurus Gregorio, Ann. de Geol. et de 



Pal., Liv. 7, p. 89. 

 1893. Clavilithcs pacliylcurus Cossmann, ibid., Liv. 12, p. 36. 



This species is the American equivalent of the Parisian C. conjunctus. 

 The early whorls are rather bulging with closely set ribs, the spaces 

 between which are concave and scarcely equal in width to the ribs. 

 The whole aspect of the shell is stouter and more compact than that of 

 C. humcrosus (pi. VIII, figs. 17, 18), and not unlike that of C. con- 

 junctus. The depressions between the ribs are often mere lines. Each 

 whorl embraces about one third of the preceding one, and the ribs are 

 continuous from suture to suture. The shelf is practically undeveloped. 



Localities: Clayborne, Alabama (Acad. Sci. 6912; Nat. Mus. 90921). 



Horizon:- Eocene (Claiborne beds). 



CLAVILITHES HUMEROSUS (Conrad). 



(Plate VIII, figs. 17, 18.) 

 1856. Clavella humerosus Conrad, Proc. Acad. Nat. Sci., vol. 7, p. 259. 



This species in its adult character is a close parallel to Clavilithes 

 parisicnsis of the Paris Basin. It differs from that species in the 

 characters which distinguish the American species generally from those 

 of the Paris Basin. The protoconch is very irregular with more or 

 less oblique whorls, a trochoid apical portion, and a projecting apical 

 point. The last whorls have a few faint and distant riblcts, and ex- 

 tremely fine revolving lines. There is no abrupt termination. 



The conch in its early whorls has rounded distant ribs swollen in 

 the middle, and with numerous revolving spirals, which are simple for 

 the first three volutions and then become increased by intercalation. 

 A slight subsutural band indicates a posterior canal. About four and 

 one half volutions are ribbed, and the sutures are deeply impressed. 

 The ribs become mere undulations towards the end of the stage, after 

 which one or more whorls of the conjunctus type with rounded shelfless 

 contour and smooth surface succeed. A few spirals may be retained 

 on the early portions of these whorls, thus forming a danicriaccnsis 

 stage. The shelf makes its appearance gradually and the contour of 

 the whorl becomes cvlindrical. This outline is fully assumed only 



