PIIYLOGENY OF FUSUS AND ITS ALLIES. 



141 



in extremely old individuals. In some highly accelerated types the 

 tiihcrculoidcs stage is dropped out, the noce following directly upon the 

 rugoides stage, the shelf often appearing in the latter stage. 



Localities: Paris Basin, numerous localities, including Chamery 

 Grignon, Montreville, etc. (M. C. Z. iioi, 1103, 1104, 1106, 1112, 1131, 

 1396, 27726, 2yy2y, 27789-27791) ; Ronca (De Gregorio) ; Grancona, 

 Italy (Oppenheim) ; " Eocaen von Nizza und Ungarn " (Oppenheim). 



Horizon: Eocene, Calcaire Grossier, chiefly middle. Erratic in 

 Sables Moyens, Upper Eocene (Deshayes). 



In the collection of the American Museum (Zit. 847) are several 

 specimens from Chaussy, France, which in ornamentation have never 

 passed beyond the I'ugosus stage. The ribs persist to the end though 

 the specimens are large. The last whorl has a shelf. The specimens 

 resemble R. clavelloides of the angulatus branch (pi. IX, fig, 22) 

 though they belong to the R. noce series. In all specimens the two 

 plications on the columella arc shown. In somewhat more advanced 

 specimens ribless whorls succeed. 



This is a case of retardation in development, the primitive stage 



being retained long {i. e., the ribs), so that the shelf appears before 



the ribs are lost. It is not a primitve form but a retarded advanced 



form. 



RHOPALITHES JAPETI (Tournouer). 



1873. Fusiis japeti Tournouer, Bull. Gcol. See. France, 2d sen, T. 29, p. 501, tab 



VI, fig. 7- 

 1897. Ftisus japeti Tournouer, Vinassa di Regny. Pala^ontographica Italica, III, 



p. 193, tav. 20, fig. 36 a, b. 

 1901. Fusus japeti Tournouer, Oppenheim Palceontographica, vol. 47, p. 216, taf. 



XXI, fig. 17. (See fig. 21.) 



This is the terminal species of this series, 

 holding the same relations to the preceding 

 species that Clavilithes scalaris holds to the 

 other members of that series from the Paris 

 Basin. The best figure is that given by Oppen- 

 heim. which is here reproduced. 



The nepionic whorls are round, with broad 

 rounded ribs separated by less than their wddth. 

 A narrow but strongly marked subsutural band 

 occurs as in R. noce. The spirals are strong 

 and numerous and appear to be all of the same 

 size. 



The ephebic whorls are smooth or but faintly 

 marked by the spirals, except on the spindle 

 where the spirals are strong. The shelf is very 

 pronounced and below it is a strong groove 

 or spiral depression. The margins of the shelf are turned upwards 

 like the rim of a saucer. The long persistence of the rugoides whorls, 

 shows that the species is terminal only to a retarded branch of the series. 



Fig. 21. Rhopalithcs 

 japeti slightly reduced. 

 (After Oppenheim.) 



