Il8 PHYLOGENY OF FUSUS AND ITS ALLIES. 



Specimen fig. 2 of plate X has two ribbed volutions followed by a 

 siihtnhercnlosus stage, with spirals and shoulder, of something less 

 than a volution. With the assumption of the cylindrical form the shelf 

 begins to project, so that the parisiensis stage is practically dropped 

 out altogether. 



In fig. 3 of the same plate is a differently accelerated individual. A 

 rugoso-tnhcrculosus stage occurs, the last ribbed whorl having a nar- 

 row shelf. A short suhtiihcrculosus stage follows, but the whorl 

 quickly becomes cylindrical, and the shelf begins to project. The 

 spirals are still retained and they occur in the last whorl where the 

 shelf projects strongly. The whorl is still convex, owing to the strong 

 constriction below the shelf. The shelf is turned slightly upward. 



Fig. 13, pi. XIII, shows a young specimen with ntgosns, snbtnhcr- 

 ailosns and tubcrculosns stages. The shelf begins to project in the 

 latter. Figs. 15 and 17 show young individuals in the snhtnbercnlosus 

 stage. Fig. 16 shows a specimen which in the early neanic stage re- 

 sembles C. snhscalaris, while figs. 18 and 19 show young specimens 

 which likewise have just passed the stage in which they had the char- 

 acters of C. snhscalaris. In the majority of specimens the suhtnher- 

 cnlosus or tubcrculosns stages occur, followed frequently by a short 

 parisiensis stage, before the shelf begins to project. In many speci- 

 mens the shelf slopes outward instead of inward. 



In the collection of the Philadelphia Academy of Sciences is a small 

 specimen of this species in which the permanent projecting shelf begins 

 almost in the first ribless volution. There are about two ribbed and 

 spirally striate volutions (rugosus stage) followed by a short ribless 

 and spirally striate volution in which there is a strong shelf (subtuber- 

 culosus stage). The characteristic projection of the shelf appears 

 immediately after this, before the disappearance of the spirals. Thus 

 the tuberculosus stage as well as the parisiensis stage is crowded out. 



Localities: Chaumery (M. C. Z. 27^60) ; La Chapelle (M. C. Z. 

 1083); Paris (M. C. Z. 1084, Bronn ; 1085, 1086 Agassiz) ; Jancron 

 (M. C. Z. 1087); Bazile (M. C. Z. 1888); Auvers (M. C. Z. 1089, 

 1090, 1091, 1092, Duval) ; Montmiraille (M. C. Z. 27786) ; Le 

 Guepelle (Acad. Sci. 6893, Cossmann). 



Horizon: Upper Eocene: Sables Moyens, lower and middle beds, 

 but not the upper (Desh.). At Coumant specimens were found rang- 

 ing from 18 to 20 and 22 centim. in length, and 65 mm. in width (Desh. 

 1866). 



CLAVILITHES MACROSPIRA Cossmann. 



1889. Clavilithes macrospira Cossmann, Ann. Soc. Roy. Mai. de Belgique, t. 24, 

 p. 173, pi. 6, fig. 7. 



This is an accelerated species in which the shelf appears early, but 

 the whorls never become cylindrical ; they rather assume a conical shape. 



