PHYLOGEXY OF FUSUS AND ITS ALLIES. IO5 



merged orradually into the embryonic, and that hence no sharp Hne 

 is to be drawn between the two. Judging from analogy with other 

 fusoid shells we are. I believe, justified in relegating this j^ortion with 

 the primitive ribs to the protoconch. 



The conch always begins with round whorls, which are ornamented 

 by coarse widely separated ribs and by strong sharp spirals. This 

 portion of the shell may be very short, and the ribs may become almost 

 obsolete or the whole shell may consist of rounded, ribbed and spiralled 

 whorls. This latter is the case in the primitive species, such as C. 

 riigostis, which might well be separated generically from Claviliihes. 



In the typical species of the genus the ribbed whorls are succeeded 

 by smooth irregular whorls of the melongcnoid type. These show 

 progressive differentiation in the various species, according to the 

 degree of acceleration characteristic of each. 



The columella is without plaits. 



The genus is confined to the Eocene. 



Type: Claz'ilithcs parisieiisis (\la.yev-KyniSiv),^= Clavilithes loiig- 

 (cviis lA\n^. (Deshayes) non-Solander. 



CLAVILITHES RUGOSUS (Lamarck). (Emend. Grabau.) 



(Plate IX, tigs. 1-8; also text fig. 15.) 

 1803. Fiigiis ntgostis Lamarck, Ann. du Mus., t. I. p. ,316. 

 1816. Fusus rugosus Lamarck, Tab. Encyc. JNIeth., pi. 425, fig. 6. 

 1823. Fusus rugosus Lamarck, Coq. Foss. Env. Paris, p. 56 (par.s). 

 1837. Fusus rugosus Deshayes, Coq. Foss. Env. Paris, t. 2, p. 519 pars, pi. 75, 



figs. 4-7. 

 1889. Clavilitlics rugosus Cossmann, Cat. Coq. Foss. Eoc. Env. Paris, p. 174. 



The protoconch of this species is papillose, the number of whorls 

 varying from three to four. It is smooth throughout the earlier whorls, 

 but marked in Iho final ( ?) portion of the last whorl by smooth narrow 

 vertical riblets which are widely separated. At first the interspaces 

 are smooth, but later revolving lines — the beginning of the spirals — 

 appear, but these do not cross the riblets. The number of riblets varies 

 from three to five. 



The conch begins with rounded whorls with strong uniform rounded 

 ribs which are rather narrow and separated by interspaces several times 

 as wide as the ribs. They are crossed by strong sharp and uniform 

 spirals of which from five to six are visible. After a volution or two 

 the spirals in the center of the whorls become stronger and sharper, 

 producing strong cusps at the crossing of the ribs. The latter become 

 stronger, broader and less defined and a subsutural band appears, 

 indicating the presence of a posterior canal. 



In the adult the ribs are somewhat less distinctly defined and the 

 subsutural band and posterior canal more profound. Intercalated 



