THIRD, OE VERMICERAN BRANCH. 159 



the pilaa, but the specimen shows distinctly that the form of the adult is more 

 compressed than in spiratissimum, with more convergent sides, and it has tuber- 

 cules. It is precisely similar to the original of D'Orbigny's Bonnardi in the Ecole 

 des Mines. Ver. Bonnardi is figured by Wright as occurring in the Turneri bed, 

 and a much more discoidal form is regarded by him as the true Conybeari and 

 figured as such. The great flatness of the whorls and aspect of the whole shell 

 in this figure are probably the effect of age. The sutures figured have senile pro- 

 portions, the abdominal lobe being of about the same length as the superior lat- 

 erals. The specimens figured by Hauer from the Northeastern Alps, and by 

 Herbich from Siebenburgen, have more convergent sides and less angular ge- 

 niculae than is common in Central Europe. The variety from Luxemburg is very 

 like the more discoidal varieties in England. 



Var. planaries. 



Amm. planaries, Fraas, MS. 



A mm. Bonnardi, Oppel, not D'Orbigny. 



Locality. — Setnur. 



The specimen in the Museum of Comparative Zoology on the ninth whorl 

 had an abdominal lobe one half longer than the superior lateral lobes, and 

 inferior lateral saddles one half deeper than the superior laterals. The in- 

 ferior lateral lobes, however, are somewhat longer than the superior laterals, 

 and the first and second auxiliaries, which show plainly on the sides, are still 

 longer than these. Thus the sutures appear to incline rapidly towards the 

 umbilicus, as in Caloceras, but this is a delusion due to the peculiar proportions 

 of the auxiliary saddles. The outlines of the superior lateral saddles are covered 

 by the involution of the whorl, instead of being in part exposed, as in Conybeari, 

 in which last, also, these saddles are apparently broader. The superior lateral 

 saddles are divided by a single marginal lobe. 



The pilaa begin to show senile characteristics on the first quarter of the tenth 

 whorl, and on the second quarter of the same whorl the abdomen has suffered a 

 diminution in breadth. Throughout the remainder of the volution there is no 

 change in the abdomen, but the pilae become obsolescent near its termination. 

 The external aspect of the adult is similar to Conybeari. 



Only one specimen of this variety occurred in Professor Fraas's collection ; it 

 is placed with BucJclandi, but its position with relation to that species was consid- 

 ered uncertain. Professor Fraas considers it a new species under the name of 

 Amm. planaries, and the sutures differ greatly from those of the specimen described 

 above, though in the form it is more like it than either of them is like Conybeari. 

 On the last volution of this specimen the pike are almost obsolete, the keel more 

 prominent, the channels considerably shallower than in the adult. The form of 

 the whorl changes somewhat and the sides tend to converge, and the abdomen is 

 narrower, but these changes are very slight, and due entirely to the obsolescence 

 of the pilaa. 



This form was at first identified with Bonnardi, D'Orb., but the examination of 



