AGASSICERAS. 99 



appeared in the Angulatus zone, the number of species on the bucklandian hori- 

 zon was evidently more limited than in South Germany, Semur, or England. 



The coroniceran series, therefore, seems to have arisen on the same level in 

 the Mediterranean province, in the South German basin, and probably in the 

 Cote d'Or. The radicals of the subseries, so far as known, do not follow the same 

 law. Cor. latum has not yet been mentioned or described as occurring in any 

 other basin than the Cote d'Or. Cor. Sauzeanum occurs, however, in northwest- 

 ern Germany, according to'Braun, and in the South German, Cote d'Or, and 

 English basins in the Upper Bucklandian bed, though in the basin of the Rhone 

 and Mediterranean province it is not recorded with certainty from any level 

 earlier than the Tuberculatus beds. 



It is possible that Cor. Jcridion may have originated in the Northeastern Alps, 

 but Neumayr and Walmer have not yet found this species in their researches 

 amono- the fossils of the Angulatus zone, and no good figure has been published. 

 The early occurrence and large number of varieties and species in the collections 

 at Stutto-ardt and Semur, and the numerous transitional varieties, also show that 

 Cor. kridion found its most favorable home either in the South German or the 

 Cote d'Or basin. The earlier occurrence of the radical of the third subseries, 

 Cor. latum, at Semur, indicates the Cote d'Or to have been the centre of distri- 

 bution for the Bucklandi subseries. The occurrence of Cor. Sauzeanum on the 

 same level in South Germany, Cote d'Or, and England shows, together with the 

 number and variety of the forms subsequently evolved, that the centre of dis- 

 tribution of the Bisulcatus subseries lay in one or the other of these basins. 



This conclusion accords with the origin and distribution of the parent series, 

 Arnioceras, and derives additional support from this fact. It is evident also, 

 from these facts, that the Mediterranean province must be regarded as having 

 been peopled with migrants from the province of Central Europe, so far as relates 

 to the subseries of this genus, and this makes it more likely that the radical spe- 

 cies of the whole series, Cor. kridion, also arose in this province. So far as known 

 its appearance in the Angulatus horizon of the Northeastern Alps is not sup- 

 ported by the presence of transitional forms, nor by the presence of Arnioceras in 

 the same horizon. The species, if a real kridion, certainly must be provisionally 

 regarded as a chorologic migrant from the west. 



Agassiceeas. 



Agas. Imvigatum appeared in the Angulatus zone of the Semur collection, and 

 was represented by numerous specimens in this fauna. It is also attributed to 

 this horizon in the basin of the Rhone by Dumortier, and is well figured by him. 1 

 In South Germany Agas. laevigatum did not appear until the Upper Bucklandi 

 bed. In England and North Germany it appeared associated with planicosta 

 above the Bucklandi horizon. This radical species, therefore, according to our 

 present knowledge, was a migrant in all of these basins, derived probably from 

 the Cote d'Or or the Rhone basin. 



1 Etudes Pal., pi. xviii. fig. 5, 6. 



