212 INFERIOR OOLITE AMMONITES. 



the species, differing in the size of the umbilicus ; and he has depicted the scarcer — 

 the more narrow umbilicate — form. 



I have made, however, the following notes concerning the specimen so figured, 

 which is now in the British Museum, No. C 1860: — "The umbilicus is drawn 

 slightly too large ; the carina of fig. 4 at the bottom and at point of re-entry is 

 not sufficiently separated from the sides of the whorl, which do not slope so 

 gradually into the carina, but are bounded by a slight flattening. The shape of 

 the aperture is rather too broad above the middle and not sufficiently triangular." 

 I would also add that the fascicled radii are rather too long and not sufiiciently 

 clubbed at their commencement to represent the characters of the species as 

 shown in my specimens. 



Haug was mistaken when he stated that this species differed from Eaugia 

 variabilis " durch den Mangel eines Hohlkiels " (op. cit., p. 670) ; but he correctly 

 enough assigned it to its true position when he placed it in the group of Am. 

 aalensis. Dr. Lycett^ at first considered this species a variety of Am. variabilis ; 

 but subsequently he separated it definitely, and gave full particulars of the dis- 

 tinction between Am. dAspansus and Am. variabilis {jugosus ?), which fully justify 

 the position he took up. The differences between Gi^amm. dispansum and Eaugia 

 variabilis (or jugosa ?) may be stated most clearly in a tabular form thus : 



Oramm. dispansum. Haugia variabilis (jugosa). 



Eibs curved on the lateral area. Eiba straight on the lateral area. 



Ribs strongly projected forwards on the ventral Eibs very little projected on the ventral area, 

 area. 



Eibs fascicled on the inner area, and forming Eibs springing directly in twos and threes 



club-shaped costa?, of which the thick end is on from rounded tubercles which are on the edge of 



the inner margin, while the thin end extends the inner margin, 

 across the inner third of the whorl. 



Sutures plain, with shallow lobes. Sutures somewhat ornate ; somewhat deep 



lobes ; large superior lateral saddle. 



Lycett's statement that " Am. dispansus probably equals in its numbers all 

 other Ammonites at Frocester Hill " is most characteristic of this species, and 

 indicates that, in reality, the selection, for a typical Am. dispansus, of a specimen 

 which I had to separate as Gramm. Orbignyi was merely an accident. 



Gramm. dispansum, however, might be thought to be a mutation of Gramm. 

 Orbignyi were it not for the existence of Gramm. metallarium. It seems, in face 

 of this fact, more probable that this species is a descendant of Gramm. metallarium, 

 and that it has developed in the normal manner — namely, that it has acquired 

 more compression, a smaller umbilicus, and finer ribs. 



Seeing that this species was delineated in Dr. Wright's monograph, I have not 



1 " Amm. of Sands, &c.," ' Proc. Cotteswold Club,' vol. iii, p. 5, 1865. 



