54 PHYLOGENY OF FUSUS AND ITS ALLIES. 



The conch begins abruptly, with round strongly ribbed whorls, 

 and strong spirals. Two of these are prominent from the beginning, 

 but the shoulder can scarcely be called flattened. In the early whorls 

 the ribs are strong and continuous from suture to suture, though most 

 pronounced at the periphery. They are less than their width apart. 

 The whorls continue rounded until after the fifth one, when the 

 shoulder concavity becomes sufficiently pronounced to cause a peripheral 

 angulation. The costas also become faint and finally disappear on the 

 shoulder, while numerous fine spirals make their appearance on this 

 portion of the whorl. 



A sectioned specimen in the collection of the Museum of Com- 

 parative Zoology has the characters of Brocchi's type of longiros- 

 tris, i. e., the ribs continue onto the last whorl of the adult shell, 

 although the whorls are rounded. The section shows well a number 

 of apical septa, a feature observed in almost every gastropod of this 

 class which has been seen. In the present specimen, the last septum 

 occupies the seventh (?) whorl, beginning three and one half volu- 

 tions from the tip and extending backwards half a volution. The 

 shell is thickened from within by the addition of layers which cover 

 the lirse and other internal markings. The septa are formed by the 

 separation of these layers from the shell and by a rapid constriction of 

 these separated portions, thus forming a bag- or cornucopia-shaped 

 end. This is generally rounded in the final portion, but sometimes 

 it is angularly pointed. This end always rests on the bottom of the 

 whorl. Six septa have been recognized, and there are probably two 

 or three more which are obscured by the thickening of the shell or 

 destroyed in the sectioning. 



Localities: Bodighera, Italy (M. C. Z. 27797) 5 Valleys about Lu- 

 ganiano, Castello Arquato, etc., Asti (M. C. Z. 1217, 27798?, 1223); 

 Voslau Vienna Basin (B. S. 5138) ; numerous localities in Vienna 

 Basin (Homes). 



Horizon: Pliocene. 



FUSUS CASTELARQUATENSIS sp. nov. 



(Plate VI, fig. 4.) 

 Comp. Homes Fusus longirostris, Foss. Moll. Tert. Wien, pi. 32, fig. 5. 



This species is to F. longirostris what F. longicaudus is to F. colus. 

 It represents, therefore, the longicaudus type of this series. The 

 earliest stages are those of F. longirostris, the whorls being round, 

 bicarinate on the periphery, though not angular and noduled as in the 

 young of the preceding species. The shoulder, however, becomes 

 concave and the ribs begin to disappear toward the sutures. The last 

 three whorls of this shell are ribless, round, except for a gentle con- 

 cavity on the shoulder, and to all appearances quite smooth. There 



I 



