56 INFERIOR OOLITE AMMONITES. 



very well preserved. Both these specimens are from Burton Bradstock. PL XIV, 

 fig. 7, gives the side view of a specimen which is difficult to place with either 

 Lioc. opalinum or comptum without further evidence. It shows a very distinct 

 change in the nature of its ribbing. It came from the same bed at Haresfield 

 Hill in which Lioc. opalinum occurs plentifully. Its test is fairly well preserved. 

 Fig. 8 shows its thickness and fairly sharp carina ; fig. 9 shows the carina and 

 ventral area a little farther back than the top of fig. 8, which is broken off. 



Liocbras ooncavdm (Sowerby). Plate II, figs. 6, 7 ; Plate VIII, figs. 1 — 4. 



1815. Ammonites concavus, Sowerby. Min. Conch., vol. i, pi. 94, lower figure 



p. 214. 

 1881. Harpoceeas concavum, 8. Buck. Ammon. Inf. Ool. Dorset, Quart. 



Journ. Geol. Soc, vol. xxxvii, 

 p. 603. 

 1885. — — Haug. Beitr. Monog. Harpoceras, Neues Jahr- 



bucb, Beil.-Bd. iii, pi. 12, figs. 12 

 a, b (a variety). 

 (Non Ammonites concavus, d'Orbigny, Dumortier, &c.) 



Discoidal, compressed, sub-carinate. Whorls sub-convex, but with the inner 

 margin slightly raised, causing the inner area to be slightly depressed and sub- 

 concave, ornamented with sigmoidal radii, which, beginning as mere lines of growth, 

 and so continuing across the inner area, become rather broad, but not prominent 

 ribs on the outer area. The ribs then die away rather quickly at the edge of 

 the ventral area, and, continuing as strise, can be traced across the carina, upon 

 which they unite at an acute angle. Ventral area acutely sloped, with the carina, 

 though prominent, not really distinct, but as if formed by the compression of the 

 sides of the ventral area. Inner margin concave, and inclined at about an angle 

 of 60°. Inclusion almost to the upper edge of the inner margin of the previous 

 whorl, forming a small, almost regularly concave, umbilicus. The termination of 

 the body-chamber is sigmoidal, 1 generally quite plain when the test is present, but, 

 with one or more constrictions, visible on the mould, caused by a thickening of the 

 test ; the length of the body-chamber is exactly half a whorl. 2 



I have here purposely confined myself to a description of the typical form of 

 this species, which I have been able to identify by an actual comparison of 

 Sowerby's type-specimen with my own, and this type-specimen of Sowerby's I 



1 No elongated lateral processes are visible at a diameter of three inches, but they probably occur 

 at an earlier age. 



2 These characters of the body-chamber are shown by a specimen which I have not thought it 

 necessary to figure. 



