FOURTH, OR CORONICERAN BRANCH. 185 



lobes and saddles are, however, serrated, not deeply divided by the marginal 

 lobes, as in the last named species. The abdominal lobe is one half longer than 

 the superior laterals, and the inferior lateral saddles exceed the superior laterals 

 in the same proportion. 



A fine suite of these specimens exists in the Museum of Stuttgardt, showing 

 the variations described above. Some are very decidedly planicostan in aspect, 

 but not more so than other specimens of Coroniceras, in which the keel becomes 

 entirely suppressed, and the abdomen is crossed by the pilse. Young specimens 

 from Behla pass through stages which repeat exactly the characteristics of Cor. 

 kridion when considerably older and perhaps full grown. One of these is labelled 

 capraries, Fraas, planicostan variety; another lot of three specimens is named 

 Damibicus, on account of their thick whorls and pilse. A large specimen from 

 Gmiind, on the last part of the last whorl, has all the characteristics of the stout 

 English specimens of var. Gaudri/i, Reynes. There is also a fragment of a much 

 older shell, the dorso-abdominal diameter of the whorl being 60 mm., which has 

 similar characters. The channels are, however, very broad and shallow, and the 

 keel also low and broad. 



Since the above and the description of var. Gaudryi were written, I have 

 found in the collection of the Museum of Comparative Zoology English speci- 

 mens of this species exhibiting the young. In these, for one or two volutions, 

 the whorls are smooth, then obscure tubercles or swellings begin to appear upon 

 the sides, which elongate into folds on the third whorl, and become distinct pilse 

 on the latter part of this whorl or the first quarter of the fourth. The external 

 resemblance to the young of Cal. Johnstoni is complete in the pilse, the com- 

 pressed or embryonic form of the whorl, and the absence of a keel ; the sutures, 

 however, do not appear to be similar. Even on the early portions of the third 

 whorl the abdominal lobe is quite long, the superior and inferior lateral lobes 

 exceedingly short, and the corresponding saddles of equal depth. From this 

 time the complication consists in the crenulation, or rather serration, of the mar- 

 gins, and the slow increase of depth in the superior lateral saddles ; the other 

 saddles and lobes remain about what they were at first with regard to their 

 proportions. The keel is perceptible as a slightly raised siphonal line on the first 

 quarter of the fifth whorl or last of the fourth. In the first of this stage, the 

 abdomen, pilae, and form of the whorls are similar to those of the adult of Cor. 

 kridion. On the fifth volution, however, the abdomen becomes flatter, the ge- 

 nicular band of the pilse more abrupt, and finally tuberculated, and the hitherto 

 divergent or gibbous sides flatter and slightly convergent. 



The young figured by Quenstedt 1 are questionable. They are more com- 

 pletely pilated than is usual in the species, and the form of the whorl is quite 

 different. We doubt the correctness of the identification. 



1 Amra. Schwab. Jura, pi. xi. fig. 15-17. 

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