154 W. IT. Hiidksfon — On the YorhsMre Oolites. 



level of the wliorl. Cast of the body-whorl showing very faint 

 traces of a carina. Other indications wanting. 



Another specimen. — From the Kelloway Eock (zone 5), Scar- 

 borough. Bean Collection, British Museum. T^pe of PL arenosa 



BEFIGUKED. Fig, 3, 



Approximate value of the spiral angle 92°. 



Though broken and imbedded in matrix, portions of the shell are 

 exquisitely preserved in spar tinged externally with brown oxide of 

 iron. Owing to the prominence of the basal girdle, the shell is 

 zoned rather than turrited. Posterior fths of each whorl flat and 

 sloping, remainder occupied by the girdle. 



The ornaments consist of a reticulate system which occupies the 

 posterior half of the whorl : in the penult this is very regular and 

 slightly tuberculated at the nodes : in the centre of the space 

 between this reticulate system and the girdle lies the band of the 

 sinus, which is narrow and salient, but less salient than the girdle, 

 which consists of four crenulated spirals welded together (see Fig. 

 3a). The cast of the last whorl visible is smooth, yet slightly 

 angular at the turn. Other indications wanting. 



Relations and Distribution. — The reticulate structure of the 

 posterior portion of each whorl, the position of the somewhat 

 narrow and yet prominent slit-band, and. the crenulated belt at the 

 base are characters of a group of Pleurotomarice, which has many 

 members. There are shells in the Inferior Oolite of Sherborne, 

 which even show a connecting link between PI. guttata and P. 

 granulata, Sow., and it may well happen that from such the 

 Oxfordian species now under consideration has been modified. The 

 varieties of Pleitrotomaria are so infinite wherever the genus is well 

 represented, that authors have hardly known where to stop in 

 naming specific forms. Hence it is possible that no absolute identi- 

 fication with continental fossils can be established in this case. 



PL dathrata, Miinst., froin the "Jurakalke" of Pappenheim, has 

 a tolerably close resemblance to the conditions represented by PL 

 arenosa, but Goldfuss's figure is an enlargement. Mr. Leckenby 

 considered that the species described by him was closely allied to 

 PL galathea, D'Orb., also an Oxfordian species. In this case the 

 spiral angle is about the same, yet in other respects there are 

 differences of some importance. On the whole I am disposed to 

 regard PL cincta (Miinst.), D'Orb., as being the nearest to PL guttata, 

 if not identical. The slightly concave angle of the spire in both 

 is very similar. D'Orbigny says that PL cincta is special to the 

 Oxfordian, occuri'ing both in J^'rance and Germany. Whether his 

 species is really the same as Trochus cinctus, Miinst., is another 

 question. 



Pleurotomaria guttata is confined, in Yorkshire, to the Kelloway 

 Eock, where it is rather rare. 



82. — Pleurotomaria anglica, Sowerby, 1816. PI. IV. Fig. 5. 



1816. Trochus similus (sic), Sowerby, Min. Conch, pi. 142 ; T. anglica in Index to 

 vol. ii. 



