Hyatt.] 398 [June 7, 



lateral ear-like expansion of the mouth edge, according to the variety 

 to which the shell belongs, will see that this is a probable inference. 

 These observations can be readily confirmed in any good collection 

 of Amm. fuscus, and show that the presence and absence of the ear- 

 like expansions may take place in forms as closely allied as the two 

 alluded to above. Intermediate forms with the lappets as a variable 

 characteristic, or as a characteristic of the adult stage of growth 

 alone, ought to ba eventually found in those varieties which approxi- 

 mate closely to subcoronatwn, if this is a correct view. 



Quenstedt alludes to large forms which have no lappets, and these 

 may have some bearing on the question, but I refrain from express- 

 ing an opinion since, unfortunately, I have not seen such examples. 

 ] would, however, mention that there are certain forms which about 

 evenly divide the characteristics of the two species, but the absence 

 of the mouth makes the reference of these to either Brdikenridgii or 

 subcoronatum doubtful. Some of the latter have the young until a 

 late period, precisely similar to the flat abdomened form of subcorona- 

 tum with the similar ribs and tubercles; and this is the general char- 

 acter of the development in the larger specimens, but in smaller 

 specimens, especially the English forms, a more contractum-like form 

 becomes apparent at an early stage, and the development approxi- 

 mates to what it eventually becomes in Sauzel. 1 



Stephanoceras linguiferum. 



Amm. lingui/erus D'Orb., Terr. Jurass., pi. 136. 



The varieties of this form fade into those of Braikenridgii by in- 

 sensible degrees, though the extreme forms differ in the larger com- 

 parative size of the whorls, the amount of envelopment, which is 

 greater than in Braikenridgii, the psculiar bent aspect of the lateral 

 ribs and the more ornate aspect of the shell, due to this arrangement 

 of the ribs, the fine abdominal ribs and the prominent tubercles. 

 The increase in the size of the shell is constant in this, and also in 

 Braikenridgii, there being no regular contractions in the size of the 

 whorls due to growth, as in Sauzei. Amm. Torricelli (sp. Oppel) 

 is a form of this species, as it appears in Moesch's collection at 

 Zurich and in the Paleontological collection at the Munich Museum. 

 Amm. Keppleri Oppel ought also, according to my views, to be in- 

 cluded under this name. 



1 Subcoronatum is merely an intermediate form between this species and the true 

 nodosum, and therefore I quote from Quenstedt's views as directly confirmatory of 

 the above. 



