96 INFERIOR OOLITE AMMONITES. 



carina on a flat ventral area is, however, a very marked feature in Hypcrlioceras 

 discites, and this alone will distinguish the one species from the other ; but, in 

 addition to this, we have the very fine, smooth texture of the test. The similarity 

 between the two forms is a slight instance of convergence. 



This is the most frequent species belonging to the genus, and is not 

 uncommon at Bradford Abbas, Dorset, in the Concavum-heds. The large size 

 which it sometimes attains is shown in Plate XVIII, fig. 1. Had this specimen 

 been obtained perfect, as it evidently was before being disturbed, it must have 

 reached the giant size of about ten inches in diameter. Even now it is the 

 largest specimen of the species in my possession. In Gloucestershire I have 

 obtained a specimen of this species from certain strata which lie above the 

 Harford Sands and below the Gryphite-grit, in the third railway-cutting west of 

 Bourton-on-the-Water Station. These strata are probably equivalent to the 

 Lower Trigonia-grit of other parts of the Cotteswolds. 1 In the neighbourhood of 

 Stroud Mr. Witchell obtained several specimens from the Gryphite-grit of Frith's 

 Quarry near Painswick, and of Rodborough Hill. Dr. "Waagen (p. 600 (94) ) 

 quotes this species from Wentzen and Dohnsen, North Germany. 



Plate XVII, figs. 1 and 2, illustrate the nearest approach in shape to Dr. 

 Waagen's figure which I have been able to obtain ; but this differs in its extremely 

 smooth test (very well preserved) showing no trace of ribbing. Figs. 3 and 4 

 represent a specimen with more ribs and an almost concave umbilicus. It shows 

 the complete mouth-border. Plate XVIII, figs. 1 and 2, illustrate an extremely 

 well-preserved adult example. It has certain longitudinal lines and other marks, 

 also the remains of an extremely thin layer of test overlying the actual outer test 

 of the whorl, 2 all of which indicate the portion covered by the body-chamber of the 

 next whorl ; and the former, in all probability, correspond to similar marks exhi- 

 bited by Amaltheus. The great increase in the width of the umbilicus in the turn of 

 a whorl is shown by the innermost of the longitudinal lines ; and this is an indica- 

 tion of where the curve of the inner margin was continued. This specimen came 

 from Anbury Quarry, 3 Bradford Abbas. Plate XVII, fig. 5, is the side view of a 



1 See p. 91. 



2 These remnants of test belonged to the inner part of the overlapping whorl, which probably was 

 broken away when the specimen was extracted from the quarry, 



3 In " Eine Studie iiber die obere Liasgrenze," Ool. Cap. San Vigilio (' Abhandl. k. k. geol. 

 Reichsanstalt,' Bd. xii, No. 3), Dr. Vacek, being unacquainted with the localities and the different 

 fades of the exposures, has (p. 129) fallen into some unfortunate mistakes. Among others, he fancies 

 that the Ammonite-bed at Babylon Hill and at Bradford Abbas are upon two different horizons, and 

 that Babylon Hill and Bradford Abbas are two very different places. This is not the case. As I 

 stated, at page 5, the one quarry is the exact counterpart of the other. The quarry at Babylon Hill 

 (otherwise called Anbury, Hanbury, or Henbury quarry) lies just over half a mile north of the famous 

 East-Hill Quarry ; while the latter is just under half a mile north of the railway-cutting in the village. 

 The strata which they exhibit are as similar in appearance as it is possible to be ; and the fauna which 



