PHYLOGENY OF FUSUS AND ITS ALLIES. 1 7 



spirals indicates tliat its immediate ancestor was of a primitive type, 

 and it must be regarded as a lateral branch from F. aciculatns. The 

 only advance, then, which this species has made over others is in the 

 subangulation of the whorls, and the strong development of the spirals. 

 Localities: London Clay, no loc. (M. C. Z. 27733) ; Barton cliff, 

 (M. C. Z. 27738) ; Muddiford Harts (M. C. Z. 1404) ; London Clay, 

 Barton (M. C. Z. 1403, 27741) ; Barton Beds, Hampshire (]\L C. Z. 



Horizon: Barton clay, Upper Eocene. London Clay (?), Lower 

 Eocene. 



Relations of the British Species of Fusus. 



Considering Fnsns porrectus nearest the primitive radicle, we may 

 place it at the base of the series of British Fusse. F . aciculatns is its 

 natural successor, though the former species seems to have continued 

 and to have been coexistent with the latter. F . acnminattis represents 

 a lateral branch from the F. porrectus line, in which senile characters 

 developed, resulting mainly in the obsolescense of ribs and the forma- 

 tion of a canaliculate suture. F. asper, on the other hand, must be 

 considered a lateral branch from F. aciculatns, although this species in 

 its accelerated individuals has in some respects become more specialized 

 than F. aspcr. These relations may be expressed as follows : 



Oligocene (North Germany). 



F. mxiltispiratiis. 



(p. 77-) 

 F. erectus. (p. 77.) 



Eocene. ; F. asper. 



F. acuminatus 



F. aciculatns. F. aciculatns. 



(British.) (French.) 



— F. porrectus. 



Fusus IN THE Paris Basin. 

 FUSUS ACICULATUS Lamarck. 



(Plate I, figs. 13, 15.) 



1822. Fusus aciculatus Lamarck. 



1824. Fusus aciculatus Deshaves, Coq. Foss. Env. Paris, T. II, p. 514, pi. /t, 



figs. 7. 8. 

 1889. Fusus porrectus Cossmann, Cat. Coq. Foss. Env. Paris, T. IV, p. 181. 



There is only one typical representative of the genus Fusus in the 

 Eocene beds of the Paris Basin. This is Fusus aciculatus Lamarck. 



The protoconch and earliest whorls of the conch are similar to 

 those of the British species. In the neanic and ephebic stages the 

 Parisian variety shows some marked differences from the normal 

 English variety. These differences are mainly of the nature of an 



