only above the Sands in black clays and shales, associated with a fauna 

 ■which is to a great extent local and peculiar. Of the Ammonites of the 

 Upper Sands A. dispansm and A. Aalemis, two of the more common forms, 

 are not Liassic, the former more especially probably equals in its numbers 

 all the other Ammonites at Frocester Hill. I -will now proceed to offer 

 some remarks upon the Ammonites, seriatim, and in the order in 

 which they appear in the table. 



Ammonites opalinus, Eeinecke. This is one of the more rare forms of the 

 genus in England, where it occurs only at the upper boundary of the 

 Sands ; in "Wurtemburg, fragments of it are stated to occur in immense 

 numbers at a somewhat liigher position at many localities. 



Ammonites dispansus, Lycett. This was long confounded ^iih.A.va/riabili8, 

 and it has only been after a comparison- of very numerous specimens of 

 both species, and of all stages of growth, that it has been found necessary 

 to separate them; their geological position is also quite distinct, A. dispansus 

 occurs only in the Upper Sands, A. variabilis does not pass higher than the 

 lowest fossiliferous bed of the Sands, both are very limited in their vertical 

 range and never occupy the same horizon. Both in the young and adult 

 conditions of growth A. dispansm is always more discoidal than the other, 

 the figure of the back more especially differs in its acute keel, the 

 tubercles upon the inner margin of the volutions are much more faintly 

 marked, and unlike those of A. variabilis they are irregular, they give 

 origin to numerous fasciated delicate sigmoidal radii ; in^. variabilis the 

 radii constitute rigid, nearly straight, and comparatively prominent 

 ribs, the septa in A. dispansus have the lobes much more simple, less 

 pointed, and less produced, the test is preserved very rarely and only in 

 young specimens, it is delicate and exhibits the fine hair like sigmoidal 

 radii much more distinctly than the casts. Specimens and firagments are 

 very abundant at Frocester Hill, at Haresfield Hill they are present but 

 are badly preserved. The largest specimen in my possession is 5^ inches 

 across, but very few exceed 3 inches. 



Ammonites Aalensis, Zieten. Perhaps none other of the group of the 

 Falciferi exhibits so great an amount of variability in the ornamentation of 

 the surface as this species does, for the most part the varieties upon which 

 its synonyms are founded have each a distinctive character, and their 

 names may be retained for as many true varieties. It has only been after 

 the acquisition of a multitude of examples that I have ventured to arrive 

 at this conclusion, and to select the thirty specimens on the tray before 

 me to illustrate all these varieties, for which pTirpose a smaller number 

 would but inadequately illustrate them. Two of these synonyms, 

 Ammonites comptus, Kein., and A. costula, Eein., have priority, but as the 

 former is only a young tumid abnormal variety, and the latter a rare 



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