250 W. H. Eudleston—On the Yorkshire Oolites. 



exception that the third keel shows some fine granulations. The 

 base has strong spiral bands slightly granulated. Fine axial lines 

 ornament the entire shell, which has the wide aperture chai'acteristic 

 of every specimen figured on the accompanying Plate (VIIL), which 

 has hitherto been described. 



Belations mid Distribution. — The specimen is unique ; but if we 

 could imagine that Littorina hiserta was ever in the habit of develop- 

 ing another whorl, the body- whorl of the present specimen is just 

 what we might expect as the result of the effort. Possibly we see 

 in the Jermyn Street fossil the effects of good keep and favourable 

 conditions upon an otherwise stunted race ; whilst the evident 

 relationship which exists between Amberleya hiserta and specimens 

 of the T. capitaneus group, from about this horizon in other districts, 

 serves on the otlier hand to show how wonderfully these forms run 

 into each other, and that a comparatively humble fossil like Littorina 

 hiserta has intimate relations with the most noble forms, Liassic 

 as well as Oolitic. 



57. — Littorina unicarinata. Bean MS. PI. VIIL Figs. 10a, h, c. 



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

 Wyke). Leckenby Collection. 



Length 18 millimetres. 



Height of body-whorl to entire shell 56 : 100. 



Spiral angle 68°. 



Shell short, conical, acute, not umbilicated. The spire consists of 

 5 or 6 whorls : outline trochiform, but somewhat inequilateral. 

 Sutural hollow of moderate width. Each whorl has two spiral belts 

 situated near either extremity. The posterior belt is close to the 

 suture, arid consists of a row of large and regular tuberculations, the 

 anterior belt forms a prominent keel (nnicarinata) , and is finely and 

 regularly granulated. The flanks of the shell are ornamented by 

 a sj^stem of very fine axial lines. In the body-whoii a third and 

 subordinate spiral belt is shown. 



Base of the shell a little less tumid than in the preceding species ; 

 outer lip rather more angular, but so much of the aperture is broken 

 away that the indications are not perfect. 



Belations and Distribution. — Prom the specimen (Fig. 9) previously 

 described this form differs in the wider spiral angle, and greater 

 inequality of the sides, in the less gaping character of the sutural 

 hollow, and the slightly more quadrate form of the aperture. Both 

 of them differ entirely from Troclms, however, in the lengthened 

 and tumid base, and in the wide and, on the whole, circular cha- 

 racter of the aperture, though they might very well, in common 

 with the whole of these Littorinas, be ranked under a section of 

 Turbo. 



As regards ornaments, X. unicarinata diifers from L. hiserta in 

 having the upper spiral band merely developed as a row of tuber- 

 culations close to the suture, and not in the form of a keel, and in 

 the absence from the whorls of the spire of any exhibition of a third 

 keel. The second spiral band predominates therefore, and gives a 



