W. S. HucUeston — On the Yorkshire Oolites. 55 



The spirals are 4, tlae nodes much extended spirally, and some- 

 what spiny (rather more so than shown in the figure), so as to give 

 the specimen an echinate aspect : longitudinals very straight and 

 well-marked. 



One of the conditions relied upon by Mr. Leckenby in dis- 

 tinguishing this form was its less rapid volutional increase (i.e. 

 smaller spiral angle), as compared with the more typical forms of G. 

 muricatiim. This appearance is doubtless increased owing to the fact 

 that one side of the type specimen is not quite clear of matrix. As 

 Mr. Leckenby's species were founded for the most part on specimens 

 in a poor state of preservation, and of very infrequent occurrence, it 

 becomes a matter of interest to ascertain how tar the peculiarities 

 attaching to this fossil are representative of forms on that horizon, 

 and how far they are adventitious. Unfortunately, I have never 

 seen any specimen of the muricatum-gvoiii:) from the Kelloway Kock 

 of Yorkshire other than this one. C. echinatum, von Buch, quoted by 

 Quenstedt from the Brauner Jura/^ delta, may be taken as the type 

 of this group, and the differences between it and the shells from 

 the Parkinsoni-Oolite of Aalen referred by the same authority to 

 '• T'urriteUa " muricata, Sow., were long ago pointed out by von Buch. 



Fig. 6. — C. muricatum, var. trilineatum. Specimen from the 

 Scarborough Limestone (zone 3), York Museum. 



Length 10 millimetres. 



Width 5 „ 



Spiral angle 25°. 



Spirals 3 in number ; nodes large and roundish ; longitudinals 

 prominent, and slightly arcuate, or more strictly speaking irregular; 

 whorls full, but flattened towards the middle, suture well marked. 



This is a unique specimen, and represents the opposite extreme to 

 such a form as Fig. 3, so far as the number of spirals is concerned. 

 Its wide angle and other peculiarities might almost entitle it to 

 specific distinction. 



Fig. 7. — Specimen from the Dogger Sands (lower part of zone 1), 

 Blue Wyke. Leckenby Collection. 



Length (restored) 12 millimetres. 



Width 4 „ 



Spiral angle 22°. 



Whorls tumid, and without flattening in the centre ; muricated 

 character not prominent. Spirals 5 ; longitudinals well developed 

 and arcuate. 



In the tumid rather than subangular character of the whorls, in 

 the very slight prominence of the upper spiral band, the shortness 

 of the spire, and the slightly larger spiral angle, there is considerable 

 divergence from the more typical forms of C. muricatum, of which 

 Fig. 2 may be regarded as a good representative. Taken by itself 

 alone, this specimen might almost be raised into a species, as one 

 would not hesitate to do, if any considerable number were found. 



1 Quenstedt, Der Jura, p. 417, pi. 67, figs. 15 and 16. 



