TURBO OR DELPHINULA. 365 



N.B. — The remainder of PI. XXX is occupied with figures of an interesting 

 group of turbinate shells, generally known to me as the Granata-group. This 

 group is confined to the Lower Division of the Inferior Oolite, and often to a low 

 horizon such as the Opalinus-zcme and the lower part of the Murchisonse-zone, but 

 is also abundantly represented in the Concavus-hed of Bradford Abbas. 



These depressed and highly ornamented " Turbos " are characterised by a large 

 and infundibuliform umbilicus. Interiorly the aperture is circular, but with a 

 subrhomboidal peristome, reminding one greatly of Delphinula, a view which is 

 further supported by the character of the umbilicus. Bean seems to have been 

 the first naturalist in this country whose attention was drawn to the subject. 

 Specimens from the Dogger were sometimes named in his MS. Delphinula 

 granata, sometimes Solarium granatum. Mr. Tawney named a species of this 

 group from the Concavus-hed of Bradford Abbas Turbo Shaleri. If, on the present 

 occasion, I adopt the double name, it must be understood that " Turbo" is only 

 used in a conventional sense, and that to my mind Delphinula is nearer the mark. 

 Then comes the question of " species." The relationship of the forms from 12 to 17 

 figured in the accompanying plate is obvious, and one might select a much larger 

 number of varieties. This is a case where the binomial system of nomenclature 

 is evidently at fault. Whatever specific name is used, in each case the word 

 " granata " should be understood. 



300. Turbo (Delphinula) Shaleri, Tawney, 1873. Plate XXX, fig. 12. 



1873. Tubbo Shaxebi, Tawney. Dundry Gasteropoda, p. 31 (23), pi. ii, fig. 3. 



Description : 



Height . . . . .9 mm. 



Width . . . . .12-5 mm. 



Spiral angle ..... 90°— 95° 

 N.B. — The largest specimen from Bradford Abbas does not exceed 14 mm. in 

 width. Specimens from Dundry, according to Mr. Tawney's measurements, seem 

 to be larger. 



Shell turbinate, widely umbilicate ; the spire is regular in some specimens, 

 gibbous in others, and ranges from one-third to two-fifths the total height. Apex 

 pointed, number of whorls five, sloping easily to a very strong anterior keel, 

 which is richly ornamented with rather fine granulations ; in some cases a second 

 keel is exposed in the penult; a fine and almost imperceptible circle of 

 granulations also lines the posterior margin. 



47 



