126 W. H. Hudleston—On the YorJcsIrlre Oolites. 



Cornbrash of Yorkshire, and the specimen in the Leckenby Collec- 

 tion is unique.' 



78. — Trochus? Leckenbyi, Morris and Lycett, 1850. Plate III. 



Fig. 7. 

 1850. Trochus ? Leckenbyi, Morr. and Lye. Gt. Ool. Moll. p. 115, pi. 15, fig. 21. 



Bibliographj, etc. — The authors appear to have had a suspicion 

 that this was a Pleurotomaria, but observed nothing upon the sur- 

 face of the whorls to indicate that such was the case. 



Description. — Specimen from the Scarborough Limestone (zone 3), 

 near Scarborough. Leckenby Collection. Type refigured. 



Height 15 millimetres. 



Width 17 



Spiral angle 85°. 



Eatio of body-whorl 50 : 100 



Shell short, conical, imperforate. Spire regular, and consisting of 

 about 5 whorls, Avhich are nearly flat : suture rather close. The 

 ornaments have suffered somewhat from attrition : they consist of 

 stout granulated spiral bands, those towards the base of each whorl 

 having a slight prominence : the system of transverse decussation is 

 somewhat obscured by the conditions of preservation. The body- 

 whorl shows a slight prominence at the margin. 



Base nearly flat, with strong spirals decussated -by radiating lines. 

 Aperture trapezoidal, depressed. 



Belations and Bistrilmtion. — No other specimen is known to me at 

 present, nor could 1 say for certain whether this is a Trochus or a 

 Pleurotomaria. 



Genus Pleurotomaria, Defrance, 1825. 



Nothing can be more complete and surprising than the contrast 

 presented by the extraordinary poverty of the whole of the Lower 

 Oolites of Yorkshire in regard to this genus, and the wonderful 

 abundance of Pleurotomaria in the Inferior Oolite of Dorset-Somerset. 

 The rich shell-bed of the Dogger, which has furnished something 

 like half the species described in this Memoir, does not contain 

 a single Pleurotomaria ; but there is one very large species allied to, 

 if not identical with PI. anglica, Sow., which is rarely found in the 

 lower portions of the Dogger, and possibly also in the Dogger Sands. 

 It is usually regarded as a Liassic species, and is quoted by Tate and 

 Blake under the title of PI. undosa and ainongst the eleven species 

 enumerated by them from the Yorkshire Lias. If not exactly the 



1 There is another specimen placed on the same tahlet which appears to me to 

 represent a smaller and more coarsely ornamented species, or at any rate a well-marked 

 variety (not figured) ; also from the Cornbrash. The following is the description. 



Jjei"-ht 10 millimetres. 



Width 8 „ 



Spiral angle 50°. 



The number of whorls is about 7 or 8. The angle of increase is very slightly convex, 

 whorls nearly flat : suture very distinct. The ornaments consist of about 7 strap- 

 like spirals, slightly granulated, and separated by vei-y narrow and shallow sulci. A 

 raised belt with spiral lines slightly granulated terminates the flank of the body- 

 whorl, thus constituting the basal periphery. Base flat ; other indications wanting. 



