PHYLOGENY OF FUSUS AND ITS ALLIES. 55 



are, however, strong spirals which are but Httle raised above the surface 

 of the shell and which arc subequally spaced. Between them are 

 froni five to three fine revolving lines. The whole surface ornamenta- 

 tion is subdued. A young specimen, locality unknown, occurs in the 

 collection of the American Museum of Natural History. Homes' 

 specimen from the Vienna basin (fig. 5) is much less accelerated than 

 the type of the species here illustrated. It may, however, be referred 

 to the same species. 



Locality: Castelarquato, Italy (M. C. Z. 27795) 5 Vienna Basin 

 (Homes). 



Horizon: Pliocene, Subapcnnine stage. 



FUSUS IN^QUICOSTATUS Bellardi. 



(Plate VI, figs. 5 to 7.) 

 1871. Fusus iiKcquicostatus Bellardi, Moll. terr. Terz. Piedmont, p. 131, pi. 9, 



fig- 3- 



This species comprises in itself a distinct series of shells which, 

 though connected by intermediate forms, show nevertheless such 

 marked stages that a lunnber of distinct species could be made. The 

 typical form of Bellardi comes nearest to fig. 6, pi. VI, while fig. 7 is 

 further advanced, being a good gerontic representative of this series. 

 Fig. 5 connects this series with F. longirostris. 



Beginning with the typical form of F. longirostris, we derive this 

 species by increasing the concavity of the shoulder, and the elevation 

 of the shoulder-angle. A distinct revolving band is formed, bounded 

 by the central and the upper primary spiral. This shoulder-angle or 

 ridge becomes more and more elevated, and the shoulder becomes more 

 depressed, so as to produce a flattening which finally culminates in a 

 depressed canal. The shell also becomes compactly coiled and in 

 consequence has a thickened irregular appearance which suggests 

 Cyrtulus serotinus, or the general characters of the advanced species 

 of Clavilithes. 



This species in its extreme form represents the gerontic character- 

 istics found in terminal members of most of the series of this class, and 

 which consists of a loss of the graceful form from a loose wrapping 

 round, as it were, of the later whorls about the earlier ones which still 

 retain the normal form and features. These later whorls generally 

 reach up on to the preceding ones, which they cover up in part or some- 

 times wholly. 



Localities: Castelarquato and places about Asti, Northern Italy 

 (M. C. Z. 27796, 1 2 16). 



Horizon: Pliocene, Subapennine stage. 



Fusus longirostris and its allies have many characters in common 

 with F. dupctif-flwuarsii and its allies, especially in the accelerated 



