98 GENESIS OF THE ARIETID^. 



kridion as occurring in the Angulatus beds, and figures a specimen. 1 According 

 to Fraas's collection, Cor. kridion certainly appeared in South Germany in the 

 Angulatus bed at Mohringen, and Qnenstedt declares it to be a rare form in the 

 Bucklandi zone. Coroniceran forms are so numerous in the Bucklandi zone of 

 South Germany and France, that it becomes difficult to determine whether they 

 were more fully evolved in the one or the other of these basins. 



Wright's tables and lists show that the English fauna was by no means so 

 rich in numbers of species and varieties as either the French or South German ; 

 and this result, notwithstanding the great size and multitude of specimens found 

 in the various localities of that basin, confirms our experience in the study of 

 collections while in England. 



The works of North German paleontologists show less thinning out of the 

 forms of this series in that direction than in any of the preceding genera. The 

 names uisidcatus, midticostaius, and the like, occur frequently. This suggests that 

 in bucklandian times the species of the Arietidoe had become hardier and more 

 able to survive in the unfavorable localities to the northward, or else the sur- 

 roundings themselves had changed and become more favorable. There is one 

 fact, however, favoring the former as the most probable conclusion. The speci- 

 mens are neither very abundant, nor are they so large, nor so generally dis- 

 tributed in North Germany as in South Germany. 



The radical of the third subseries of Corniceras, Cor. Sauzeanum, did not appear 

 earlier than the Upper Bucklandi bed in any fauna, not excepting that of the 

 Mediterranean province. 2 Chapuis and Dewalque show that Cor. Sauzeanum per- 

 sisted in the Luxemburg region, and that Cor. bisvlcatum and multicostatitm were 

 also present ; but the number of forms found there are certainly very limited. 

 Schlonbach mentions the usual fauna of the Bucklandi zone in Brunswick, but 

 the species are not so numerous as in South Germany, and no note is made of 

 their abundance. The absence of the Tuberculatus bed, or its unfossiliferous 

 character when present, is noted by Schlonbach, and this indicates a decrease in 

 number of forms as compared with other regions. Brauns in " Hannoverische 

 Jura," and Emerson in " Liasmulde von Markoldendorf," show that the coroni- 

 ceran series is represented, but is not remarkable for the number of species, and 

 in most localities, so far as we can learn, the species of this series are not 

 abundant. Shliiter cites Cor. rotiforme and Cor. Cmuendense as occurring in the 

 Bucklandi zone of the Teutoburger Wald, and his descriptions support these 

 results. He alludes to other forms than these species, but does not enumerate 

 them. 



The poverty of the later beds of the Lower Lias in North Germany, and the 

 constant recurrence of unfossiliferous strata, are characteristics similar to those 

 of the basin of the Northeastern Alps, and these facts indicate that similar un- 

 favorable conditions obtained there. 



Dumortier's work enables us to see, also, that in the Rhone basin on the 

 southern side of the Cote d'Or the fauna thinned out. Thus, though Cor. kridion 



1 PI. xviii. fig. 3, 4. 



2 See Mojsisovics's mention of the zone of Amm. Sauzei, Gebirgsgr. d. Osterhornes, p. 199. 



