FOURTH, OE COEONICERAN BRANCH. 175 



First Subseries. 

 Coroniceras kridion, Hyatt. 



Plate III. Fig. 3, 3. Summ. PI. XII. Fig. 9. 



Amm. kridion, Ziet., Verst. Wiirt., pi. iii. fig. 2. 



Amm. kridion, Hauer, Ceph. Nordostl. Alpen, pi. iii. fig. 4-6. 



Localities. — Seniur, Stuttgardt, Balingen. 



The pilge were already visible on the first part of the third whorl, but when 

 they began could not be ascertained. On the first quarter of the third whorl 

 the flattened abdomen of the younger volutions became more elevated, and the 

 keel was introduced. The keel continued to increase in prominence thereafter, 

 but the channels, which are faintly visible on the fourth whorl, only broaden out, 

 and do not sensibly increase in depth, after they reach the last part of the fifth 

 volution. 



The form acquired on the third or fourth whorl is carried throughout life, the 

 sides curving evenl}* from the dorsum to the abdomen ; the abdomen is elevated, 

 the pilae are either overhanging or slightly tuberculated on the latter part of 

 the third whorl, but very soon the curvature becomes equal and the tubercula- 

 tions disappear, though the geniculje sometimes remain very prominent even on 

 casts. There are three specimens of this species in the Museum of Stuttgardt, 

 the exact position of which, with relation to Bucklandi, is considered uncertain 

 by Professor Fraas. The young in all these specimens are smooth, and precisely 

 similar to the young of the specimens from the Angulatus bed, from which the 

 adults, however, differ slightly. The tubercular processes on the casts, as in all 

 other specimens of this species, are blunt, and covered smoothly by the shell, not 

 protruding into spines. The specimens in the Bucklandi bed have longer, 

 stouter whorls, with different sutures, but these differences are not sufficient to 

 separate them ; they are probably closely allied direct descendants. 



Oppel claimed to have had the original of Zieten's description, and, according 

 to him, it is a species like Conyleari, which is found with and under Bucklandi. 

 The above is the only species answering to this description and agreeing with 

 Zieten's figure in having tuberculated pilse, slightly divergent sides, a raised 

 abdomen, and prominent keel. There are no channels in Zieten's figure, but his 

 specimen was young, and even in the full-grown kridion they are very shallow. 

 Two adults and three young specimens from Mohringen, labelled Bodleyi (No. 

 3977), are in the Museum of Stuttgardt, from the Angulatus zone. The casts 

 appear to be identical with Amm. Ccqvotinus D'Orb., but the apparent tubercles 

 were merely covered smoothly by the shell, and not continued out into points. 

 Besides these specimens there is a fossil from Filder (No. 3978), which is precisely 

 like Zieten's figure, 1 and confirms these identifications. 



Though there is close approximation in the characteristics of the young in 

 most forms, there are sometimes differences. The young of the normal forms 



1 Zieten's original T was not able to see ; it could not be found in the Museum at Munich during 

 in v visit. 



