196 W. H. Hiidleston — On the Yorkshire Oolites. 



Iterations and Distribution of Alaria trifida. — But little more need 

 be said on this subject, which would require very extensive treatment 

 in order to do it thoroughly. It may be useful to recapitulate the 

 chief points in which the Yorkshire specimens differ from those of 

 Al. bispinosa, selecting in both cases our examples from the " chert" 

 bed of Kelloway Eock, as being identical in status. 



As regards the whorls of the spire, the keel is less sharp than in 

 Al. bispinosa, and the lower half less constricted : the spiral lines 

 are also finer throughout. On comparing the body-whorls, the 

 difference is immense : in AL trifida the lower keel is largely 

 developed, supporting a stout digitation which is connected by a wide 

 expanse of wing with the tail, which itself commences to curve at 

 once. Unfortunately there are no available specimens of A. bispinosa 

 with a complete tail from the Yorkshire beds. It would appear to 

 proceed nearly straight for a considerable distance, and then probably 

 terminates with a sharp anterior curve, as is the case with some 

 specimens from the Oxford Clay of the South of England which I 

 refer to Al. bispinosa. But the chief difference consists in the absence 

 of a second, or lower lateral finger in Al. bispinosa. Granted that 

 there are cases where such a process might be broken off, it is at least 

 singular that where certain conditions are noticeable, amongst which 

 is a marked attenuation of the lower keel, no lower finger can be 

 found. Practically, whether wide-angled or narrow-angled, specimens 

 of Al. bispinosa always have a feebly-developed lower keel, which has 

 every appearance of being about to terminate at the margin. This 

 is most certainly the case in the very vigorous specimen (Plate VI. 

 Pig. 10), where the upper keel carries one immense curved finger, 

 and the lower keel reaches the margin almost aboi'ted. To sum up, 

 Alaria bispinosa is a Pasha of Two Tails, and Alaria trifida is a 

 Pasha of Three Tails. 



Alaria trifida is rare • in the Kelloway Rock, but rather more 

 abundant in the Oxford Clay of Scarborough Castle Hill. 



41. — Alaria myurus (?), Deslongchamps, 1842. Narrow variety. 

 Plate VII. Fig. 6. 



1842. Bostellaria m^/eo'MS, Deslongchamps. Mem. Soc. Linn, Norm. vol. vii. p. 



176, pi. ix. figs. 23, 24, 25, 

 18 — . Alaria myurics, Deslong. Piette, op. cit. p. 30, pi. 2, figs. 8-11. 



Compare also — 

 1850. Alarta Imvigata, Morr. and Lye. Grt. Ool. Moll. p. 17, pi. 3, fig. 3. 



Bibliogf-aphy, etc. — Not admitted as British by Morris in his * 

 Catalogue. According to Deslongchamps, its occurrence is limited, 

 in Normandy, to the Inferior Oolite, where it is rare. As to Morris 

 and Lycett's species, Al. Icevigata, from the Great Oolite, the absence 

 of stri93, on which they relied as a distinguishing feature, is simply 

 due to the nature of the matrix, and is of no value whatever.^ If, 

 as they tell us, this is the only difference, then Al. myurus, Desl., is 

 a fossil of the Great Oolite, and Al. Icevigata has no justification. 



^ The Minchinhampton fossils, though very beautiful and often entirely preserved, 

 are not exactly favourable to the study of ornamentation of the finer kind. 



