FOTJKTH, OE CORONICERAN BRANCH. 183 



Wright's visit to his collection. Quenstedt's huge specimen, 700 mm. in diam- 

 eter, noted above, is described * as having the pike obsolescent near the termina- 

 tion of the last volution, and the keel as showing but little above the almost 

 obsolete channels. This, therefore, is an extreme example of senile degeneration 

 in the clinologic stage, but it has not yet reached the nostologic stage. 



Coroniceras Gmuendense, Hyatt. 



Plate V. Fig. 4-9. Plate VI. Fig. 1, 3. Sumni. PI. XII. Fig. 14. 



Amm. Gmuendense, Oppel, Der Jurafor., Wurt. Jahreshf , XII. p. 200. 



Amm. Brooki, Ziet., Verst. Wurt , pi. xxvii. fig. 2. 



Aster, tenue, Hyatt, Bull. Mus. Comp. Zobl., I. No. 5, p. 79. 



Ariet. Crossi, Wright, Lias Amm., p. 283, pi. x. fig. 1, 2. 



Localities. — Semur, Gmund, Gdppingen, Aalen, Aargau. 



The adults of this species are readily distinguishable from Cor. lyra by the 

 smaller size of the whorls, the characteristics of the sutures, the extreme narrow- 

 ness of the abdomen as compared with the dorsum, and the broad, shallow chan- 

 nels. The keel is more prominent also than in Cor. lyra, and the pike end very 

 abruptly Avith geniculse or pseudo tubercles. This peculiarity is observable on 

 the latter part of the sixth whorl, and the bending forward of the genicidae, as 

 they rise on the narrow abdomen, is hardly observable on the cast until after the 

 completion of the seventh whorl. On the eighth volution the genicular become 

 less prominent on the cast, and the depressed genicular and pilae form a single 

 arch slightly interrupted by the tubercular aspect of the former. These charac- 

 teristics are not altered when the shell is present, but have about the same ex- 

 pression as upon the cast. The genicular on the seventh whorl, in one specimen 

 examined, are prominent, and their forward bend plainly observable, though 

 without tubercles. 



The abdominal lobe is broad and deep (Plate V. Fig. 5). The superior lateral 

 saddles and lobes are nearly obsolete, the inferior lateral lobes and the first aux- 

 iliary saddles are but slightly developed. On this account the inferior lateral 

 saddles, which are of about the usual size, acquire remarkable prominence. 

 We have already noticed, in variety C of Cor. rotiforme, a tendency towards the 

 suppression of the superior lateral saddles, and here it is actually carried out. 

 The marginal lobes and saddles of the superior laterals, however, remain on one 

 specimen from Aargau, but on one from Semur only the inner of the three sad- 

 dles is of noticeable size. These characteristics are present in the adults of this 

 species, and consequently are not due to old age. 



On the latter part of the eighth whorl the pilae lose their tubercles, (Plate V. 

 Pig. 5,) and the genicular become almost obsolete, being reduced to curved con- 

 tinuations of the depressed arched pilae, which are most prominent at the um- 

 bilical shoulders. The channels continue to be very well defined, though much 

 shallower, (Plate V. Pigs. 8, 9,) and channel ridges are preserved until the first 

 quarter of the tenth whorl. On the second quarter of this whorl the pilae are 



1 Amm. Schwab. Jura. p. 115. 



