niYLOGENY OF FUSUS AND ITS ALLIES. lOI 



shelf is short, the whorls quickly becoming cylindrical. In this respect 

 this shell approaches ClavcUofusus uiacrospiratus. Fig. i6, pi. I, is 

 a young shell of ClavcUofusus, still in the ribbed (Fiisiis) stage, which 

 may belong to this species. 



Localities: Paris I'asin (M. C. Z. 27731. 1098) ; Soissons (M. C. Z. 

 1099, 1100) ; Chaumery (M. C. Z. 27746) ; Cuise Lamotte (M. C. Z. 

 27750) ; .Montmiraille (M. C. Z. 27785) ; Comprigne (M. C. Z. 1096, 

 Type). 



Horizon: Lower Eocene. 



CLAVELLOFUSUS TUBERCULATUS sp. nov. 



(Type Plate I, fig. 19.) 



(See also figs. 18 and 22. Plate I.) 



This species is less accelerated than the preceding, which passes 

 through the stage at whicii this species stops. The early stages are 

 as described for C. spiratus, there being six or more of the ribbed whorls 

 (counting those which are broken away). In the last two whorls 

 before the shell becomes smooth the ribs gradually become obsolete, 

 finally disappearing altogether. The spirals, however, continue for 

 a time. This gives two short stages comparable to the damcriacensis 

 and conjunctiis stages in the Clavilithcs series. 



Thus, the penultimate whorl is free from ribs, but marked by 

 spirals. It is rounded and is closely appressed to the preceding one, 

 there being no sutural shelf. This may be compared to the sitb- 

 conjnnctns stage. The spirals gradually become obsolete, the shell 

 then being comparable to Clavilithcs conjunctiis. Before the complete 

 disappearance of the spirals, the sutural shelf appears, which is char- 

 acteristic of the last whorl, this retaining its convex contour, but being 

 free from spirals. This is the adult stage of this species, judging from 

 the size of the shell. It corresponds to the late neanic or early ephebic 

 stage of C. spiratus which passes beyond in the adult stage, where it 

 assumes a cylindrical form of whorl. 



Specimen fig. 18 (pi. I) may represent a young of a somewhat ac- 

 celerated individual of this species, though it is perfectly possible that 

 it might in the adult have assumed a cylindrical whorl, and thus be- 

 come a C. spiratus. The ribs become obsolete in about the sixth 

 whorl, the spirals disappearing shortly after. The shelf appears 

 shortly after the disappearance of the ribs, the contour of the whorl, 

 however, remaining convex. The shell, therefore, is in the tiibcrculatiis 

 stage. Specimen fig. 22 is likewise in the tiibcrculatus stage, and 

 judging from the strong convexity of the whorls probably represents 

 an immature ClavcUofusus tiibcrculatus. The shelf appears very soon 

 after the disappearance of the ribs, the spirals becoming very faint on 

 the ribless whorls. Fig. 18 is from Soissons, fig. 22 from Cuise. 



