niYLOGEXY OF FUSUS AND ITS ALLIES, 85 



protoconch stage, which nia\- then l)e considered as highly accelerated 

 as that of Fusns. 



As the shell grows older the shoulder ahove the central spiral 

 gradually becomes flattened, the angulation grows more pronounced, 

 and finally flattened spines take the place of the simple carina. The 

 ribs at the same time gradually become obsolete below the shoulder 

 angle, and later on upon the shoulder as well. Slight undulations, 

 however, mark the places where the ribs would cross the carina, and 

 on these the flattened spines are prominent. The shoulder is marked 

 by three strong spirals with interspaces decreasing in width tow^ards 

 the suture. Sometimes two additional finer spirals crowded close to 

 the suture and near together occur on the adult shell. Only two 

 spirals of the body of the whorl are visible above the suture, and in 

 some cases the lower of these is covered up by the edge of the suc- 

 ceeding whorl, leaving only one visible. This latter with the central 

 spiral developed into a carina, and with the first spiral above the carina 

 constitutes the three primary spirals. 



In the final portion of the last whorl of a large and probably 

 gerontic individual of this species (pi. I, fig. 9) the spines of the 

 angle become fused into a strong carinal ridge. The lines of growth 

 at the same time become lamellose, and the aperture is slightly con- 

 tracted. 



Throughout the majority of the later whorls, i. e., in both neanic 

 and ephebic stages, the shoulder suddenly turns up below the suture, 

 forming a narrow subsutural band and marking the early development 

 of a posterior canal in the aperture. This feature, which does not 

 generally occur in the Eocene Fusi, is an additional indication that this 

 species in its own genus is further developed than are the Eocene Fusi. 



The lines of growth of F. (f) scrratiis on leaving the suture are 

 at first straight for the width of the subsutural band, then curve quite 

 abruptly backward, and. after crossing the shoulder angle, curve again 

 gently forward. 



This species strikingly recalls Fiistts brcdcu Michelotti of the 

 Italian Pliocene. It was apparently not until that later period in the 

 Tertiary that true Fusns reached that stage of development which the 

 present species had reached in the Eocene. 



Localities: frames (M. C. Z. 1398, 27739) ; Epernay (M. C. Z. 

 1397) Paris (M. C. Z. 1399, 1405). 



Horizon: Eocene, Galcaire Grossier. 



The protoconch of this species diflfers to some extent from that of 

 F. mcycn. The first whorl is like that of a true Fusits in some respects, 

 while the second partakes of the nature of that of F. mcveri. It is 

 most probable that the present species has originated entirely inde- 

 pendently of the American Fusoid shells, probably from some Pleuro- 



