128 W. H. EucUeston—On the YorUhire Oolites. 



Heis^lit 24-5 millimetres. 



Width 26 „ 



Spiral angle 78°. 



Eatio of body-whorl 48-100. 



Shell short, step-like, with the rudiments of an umbilicus. Body- 

 whorl about half the height of the spire. Whorls about 6 in number, 

 angular, sloping in the posterior two-thirds, nearly vertical {i.e. 

 parallel to the axis) in the anterior third. The ornaments consist of 

 numerous fine spirals which present nodes at the points of contact 

 with the fine transverse lines which decussate them, the result being 

 a very pretty reticulation with a fine mesh. The spirals are not 

 exactly of equal strength : for instance there is a hollow beneath the 

 carina, in the bottom of which is a very fine spiral line quite plain ; 

 a little distance below this, and almost at the base of the whorl, a 

 pair of strongly granulated spirals constitute the rudiments of a belt 

 or lower carina. (Some of these features can only be recognized in 

 exceptionally well-preserved specimens.) The principal carina, 

 which occurs about two-thirds down, carries the imbricated slit-band ; 

 this occupies the most salient position in each whorl. 



Base tolerably tumid, with strong spiral ornaments, less conspicu- 

 ously decussated than on the flanks of the shell. Aperture sub- 

 quadrate or trapezoidal, columellar lip thick and curving forwards. 



Another specimen. — Kelloway Eock (zone 5), Scarborough. Leck- 

 enby Collection. Fig. 9. 



The condition is not favourable for close description ; moreover, the 

 specimen has the appearance of having been slightly compressed. 

 The outline and ornaments are sufficiently distinct to make it clear 

 that there can be no differences of importance from average Corn- 

 brash specimens. The position of the slit-band in the keel at the 

 angle of the whorls is also equally obvious. If there is any struc- 

 tural difference, it consists in the slightly more sloping outline of the 

 anterior third ; but this I consider to be the result of compression. 



Another specimen. — Oxford Clay (zone 6), Scarborough. York 

 Museum. Fig. 10. 



Still more compressed than the last, and in what may be termed 

 a " half-cast " condition, though better than many fossils from the 

 " Oxford Clay" of Scarborough Castle Hill. The nodes at the inter- 

 sections having been worn nearly flat, the ornaments are in a reticu- 

 late condition, and this is also the case with the Kelloway Eeck 

 specimen. 



N.B. — Very large specimens from the Cornbrash have a height of 

 4:\ centimetres, and such are slightly more pyramidal than the 

 average forms. A specimen in Mr. Leckenby's collection must have 

 had 9 or 10 whorls, and there is a somewhat similar specimen in the 

 Scarborough Museum. In these large specimens the "granulate" 

 character is almost entirely efliaced, and the " reticulate" character 

 prevails. 



Belations and Distrihntion. — The relations of a thoroughly demoid 

 type are pretty wide, though no species of Pleurotomaria resembling 

 this one occurs on any lower horizon in Yorkshire. But, as we have 

 seen, it is easy to trace this form upwards through the Kelloway 



