114 



INFERIOR OOLITE AMMONITES. 



In his ' Monograph on the Lias Ammonites,' 1 Dr. Wright has recorded 

 Harpoceras bifrons from the Cotteswold Sands at Frocester, and he places these 

 Sands in the " zone of Harpoceras bifrons /' but he seems to have been somewhat in 

 doubt upon the matter, since he places the Sands of all the other localities in the 

 " zone of Lytoceras jurense" and at p. 140 says that Harp, bifrons is a leading 

 fossil of the clay-bed of the Upper Lias, but is not found in the Jurense-zone unless 

 as a fossil washed out of an older bed, and redeposited 2 in a newer formation. 



It is probable that in making geological divisions we ought not to lay too much 

 stress upon the occurrence of this species, even so plentifully in the Cotteswold 

 Sands, since Dr. Haug 3 remarks that it occurs not infrequently in the Jurense-zone, 

 and even comes in the Opalinum-zone. What we shall really have to consider in 

 this matter is the other species which accompany it in these Sands. At the same 

 time it is probably preferable to use the term Commune-zone to designate the 

 zone in the Upper Lias which succeeds that of Harp, falciferum, instead of 

 employing the name of an Ammonite (bifrons) which seems to have so wide a 

 vertical range. 



About forty feet from the base of the Cotteswold Sands, at Coaley Wood, in a 

 bluish-grey sandstone, reposing upon and followed by bright yellow micaceous 

 sands (Bed 17, section 6, p. 45), is the chief place at which I have obtained this 

 compressed, involute variety. Plate XXII, figs. 30, 31, represent the side and 

 front views of a young specimen of this variety. In Plate A, fig. 28 marks the 

 suture-line, taken from a specimen of the same variety obtained in the Cotteswold 

 Sands. To compare with this is fig. 29, which shows a suture-line taken from a 

 thick, evolute specimen, obtained in the Upper-Lias Clays of Trent, Somerset. 

 The difference of the disposition of the inner part of the two suture-lines will be 

 noticed, as well as the greater length of the part inside the inferior lateral lobe of 

 fig. 28. 



1 Palseontographical Society, vol. xxxiii, p. 138, 1879. 



2 At Coaley Wood, I think, no idea of re-deposition can be entertained. The great number of 

 specimens, the complete manner in which they are preserved, with the test, and in some cases the 

 mouth-border complete, does not admit of this opinion being held. 



3 Op. cit., p. 641, 1885. 



