206 INFERIOR OOLITE AMMONITES. 



to the ventral area may be noticed in many figures in this Monograph, and, 

 with regard to this group of Ammonites, in Pis. XXXIV — XXXVI ; and I have 

 frequently referred to this matter in the text (pp. 81, 82, 87, 203). 



Under the name Grammoceras fallaciosum I have thought it most convenient 

 not only to include the forms named by Denckmann, Am. Bingmanni and 

 Am. Struckmanni, but also the form which Dumortier and Bayle figured under the 

 incorrect specific name of Eseri. The differences betweeen them and Gramm. 

 fallaciosum are very slight and inconstant, consisting of a variation in thickness, 

 size of umbilicus, and flexure of ribs. These forms may, in my opinion, be best 

 treated as varieties as under : 



Gramm. fallaciosum, sensu stricto (PI. XXXIII, figs. 17, 18). Fine, fairly 

 straight ribs. 



Var. Bingmanni (PI. XXXIV, figs. 3, 4). Thicker and squarer, with coarser 

 ribs. 



Var. Struckmanni. Larger umbilicus, whorls not so high and more slowly 

 coiled ; thinner than Bingmanni. 



Var. CottesiooldicB (PI. XXXV, figs. 4—7; PI. XXXIV, figs. 10, 11). Higher 

 whorls and a smaller umbilicus than the others ; also more compressed. 



Of the delineations given in Dr. Wright's Monograph, figs. 1 — 3, pi. Ixiv, 

 appear to me to represent Gramm. fallaciosum though it is rather coarsely-ribbed ; 

 while figs. 5, 6 illustrate an adult var. Bingmanni. In pi. Ixxiv, figs. 1, 2, is 

 depicted a splendid specimen of the var. Struckmanni, with test and carina pre- 

 served and also the termination. PI. Ixxxi, figs. 4 — 6, represents what would 

 seem to be another variety of this species. It is a form which none of my 

 specimens match exactly; and, though much like Gramm. fallaciosum, it has a 

 smaller carina and a smaller umbilicus. 



The following notes concerning Gramm. fallaciosum and its varieties^ may be 

 of service : 



Fallaciosum. Bayle's figure of the type represents a form with numerous very 

 straight ribs. The side view is excellent ; but the other view, not being quite full- 

 front, prevents a correct appreciation of the thickness of the specimen. No text 

 has been published concerning these plates. 



Bingmanni. Denckmann gives us three views of immature specimens of this 

 form. The specimen represented in his pi. v, fig. 4, has a larger umbilicus and 

 finer ribs than the specimen in his pi. vi, fig. 5. Of the latter no front or back 

 view is given. Concerning these figures he says (p. 71), " Dem Am,m. Sxmanni 

 nahe verwandt, unterscheidet sich Amm. Bingmanni von diesem leicht durch starkere 



' I have obtained two more varieties ; one like Bingmanni but thinner, yet more involute than 

 Struckmanni ; the other similar, but the whorls slope more to the carina, giving the aperture a sub- 

 triangular appearance. 



