62 INFERIOR OOLITE AMMONITES. 



friends for identification. Its occurrence in any of these places would be ex- 

 tremely interesting from a geological point of view ; and my idea is that it should 

 be sought for in the Lower Trigonia-grit of the Cotteswold area. Mr. Hudleston 

 (' Gasteropoda,' Pal. Soc.,pp. 27,44, 1887) states that this species 1 is characteristic 

 of the " Maliere " of Normandy, and Dr. Haug (loc. cit., p. 684) says that it 

 occurs in the Soiverbyi-zone in the Jura of Berne. 



Plate II, figs. 6, 7, represent the actual type of the species, since it is the 

 specimen originally figured by Sowerby, now redrawn. It is in the British 

 Museum (Natural History Branch). The artist has made the breadth of the 

 aperture at the inner area too great, and has failed to delineate the characteristic 

 concavity in the inner area, which, however, is to be noticed in fig. 6. The inner 

 margin is also shown convex instead of concave. 



Plate VIII. figs. 1, 2, show the typical form of this species, of a somewhat 

 larger size, collected by my father at Bradford Abbas, Dorset. 



Plate VIII, figs. 3, 4, illustrate a younger specimen, but with finer ribs than 

 the above forms apparently possess ; otherwise it is similar. This has one of the 

 most perfect tests that I have seen. It came from Bradford Abbas, Dorset, and 

 is in my collection. 



The life-zone in the Bradford Abbas district, which Lioc. concavum and its 

 varieties dominate in point of numbers, is the bed No. 5 of my section at page 5. It 

 is here a yellowish-brown stone, with darker grains, or sometimes inclining to blue 

 with similar grains. In the partings it weathers to a soft yellow paste, from which 

 shells are very readily extracted ; but the bed altogether generally yields specimens 

 in an extremely good state of preservation, and the matrix can be chipped cleanly 

 away from the tests, thus differing from the " Paving-bed " (3furchisonce-zone) 

 below, which sometimes very closely resembles it in colour and texture. It is 

 seldom that specimens in the Concavum-hed are at all perished ; but this condition 

 is not unfrequent in the Paving-bed. At Halfway House the Concavum-hed is 

 very similar ; but at Louse Hill and at Wyke Quarry, in both of which it is the 

 chief " fossil-bed," it is rather harder, of a bluish colour, with light yellow 

 grains, often very few of them. It does not yield specimens in as good condition 

 as at Bradford Abbas ; and, when exposed to the weather, they deteriorate 

 from decomposition very much sooner. At Corton Downs 2 the same horizon 

 exhibits quite a different character, being a blue clayey marl with bands of 

 stone. Lioc. concavum and Ammonites in general are scarce here, and are 

 found without any test and frequently crushed. They partake of the blue' 

 character of the matrix. Brachiopoda are abundant and well preserved, and are 



1 As the species he refers to seems also to go by the name Am. aalensis it is possible it may 

 be my Lioceras ambiguum (see p. 28), and if so has a peculiar bearing on my remarks, p. 64. 



2 Marked as Horethorne Down on the Ordnance Survey Map. 



