W. H. Hudleston — On the Torhahire Oolites. 157 



bitt I have not seen it. Phillips' figure is fairly characteristic and 

 leaves but little doubt that it represents one or other of the twn varie- 

 ties of Trochotoma, which are not absolutely uncommon in the Dogger. 

 The absolute identification would be interesting, because D'Orbigny 

 regarded Phillips's species as a Pleurotomaria, contrary to the opinion 

 of English palaeontologists since the days of Morris and Lycett. It 

 is true that the indications of the loop are not very clear in the 

 Dogger specimens ; still there are indications. 



It can hardly be doubted that the most suitable name for this 

 section of Trochotoma would be T. gradus ; in that case there might 

 be room for some of the other names as varieties, local or otherwise. 



Descriptions. — Specimen from the Dogger (zone 1), Peak (Blue 

 Wyke). York Museum. Figs. 6, 6a, 66. 



Height , 16 millimetres. 



Width 24 ,, 



Spiral angle about 90°. 



Shell trochiform, tabulate, and profoundly excavated ; height to 

 width as 2:3. The whorls, about 5 or 6 in number, are nearly 

 rectangular, the posterior area being flat and unchannelled, with a 

 close suture. The whorls of the spire show only one keel, which is 

 situated at the angle, and carries the fissure band in its flat upper 

 part. The body-whorl presents something of the nature of a lower 

 keel, which forms the basal margin, the space between the two being 

 rather excavated ; hence the body-whorl is bicarinate. 



A very regular system of spiral lines pervades the entire shell, 

 including the base ; with slight curved axial decussation in parts of 

 the body-whorl, due perhaps to growth. 



Base enormously excavated : aperture depressed, but too indis- 

 tinctly preserved to show its true chai'acters : neither can the loop 

 be recognized with absolute certainty, N.B. — The peculiar rise of 

 the carina in the body-whorl of the specimen, which converts a 

 portion of the posterior area into a sort of channel or gutter, may 

 have had some connexion with the position of the loop, or it may be 

 accidental. 



Another specimen. — Same horizon and locality. Leckenby Collec- 

 tion. ISiot figured. 



Height 11 millimetres. 



Width 26 ,, 



In nearly all respects similar to the preceding, but less depressed : 

 the whorls of the spire also are more exposed, so as to show some- 

 thing of the lower keel, which in the previous specimen is only seen 

 in the body-whorl. 



Belations and Distribution. — The difi^erences between Trochotoma 

 gradvs, Desl. [T. bicarinata, D'Orb), T. affinis, Desk, T. carinata, 

 Lye, and T. calix, PhiL, are such that they may well be disposed of 

 under the head of varieties. The specimen figured approaches pretty 

 nearly to T. gradus, whilst the specimen described, but not figured, 

 approaches more nearly to T. affinis, Desk, in being less depressed. 

 I should be disposed to consider that the general run of specimens 

 in the Dogger are not quite so flat and depressed as T. gradus, but 



