J. S. GARDNER ON THE CRETACEOUS DENTAL1ID2E. 63 



bordered by 2 sharp and clear angular keels ; the ventral surface 

 slightly convex, with a depression in the centre, and with a rounded 

 rib at each angle bordered on the inside by 2 other longitudinal ribs. 

 These 2 lateral ribs and a central furrow alone are present at the 

 apex, which is minute and cylindrical. The angularity and the 

 ornament diminish towards the aperture, especially on the convex 

 surface. The aperture is cylindrical and very slightly constricted, 

 with thin margin. L. -4307 in. B. -0625 in. 



When crushed this shell appears deeply grooved. It is more regu- 

 lar, smoother, and less curved than the species next described, from 

 which it also differs in texture. I have not observed any grooves or 

 notches in the apex ; but the angulated form and constricted aperture 

 leave no room to doubt that it is correctly placed in Siphodentalium. 



It is very closely allied to S. quinquangulare of Forbes and S. 

 tetragonum, Brocchi, both of which, however, present specific 

 differences. 



It is abundant in the Gault at Folkestone. 



Siphodenialitjm cuRvuM, sp. nov. Gault. (Plate III. figs. 45-47.) 



Shell minute, much curved, cylindrical interiorly, quadrangular 

 exteriorly, the angles forming sharp prominent ridges, which com- 

 mence from the apex and continue to the aperture ; between them 

 are concave regions strongly marked by rings of growth ; aperture 

 round and slightly constricted, margin thin ; apex small. The 

 amount of curve, usually great, is variable, and the shell often 

 irregular. Greatest length • 625 in. B. -0625 in. These dimensions, 

 it should be observed, are seldom attained. 



This shell may easily be confounded with some of the young of 

 the polygonal Serpulce, which are also met with in the Gault. Still 

 there appears little doubt that it is a true Siphodentcdium. 



It is not uncommon in the Gault at Folkestone ; and Mr. Meyer 

 possesses a specimen somewhat broader, but apparently of the same 

 species, from the top of the Atherfield beds at Sevenoaks. 



Genus Cadtjlus. 

 Cadulus gaultinus, sp. nov. Gault. (Plate III. fig. 48.) 



Shell minute, thin, elongated, cylindrical, contracted at each end, 

 swollen ; curve of the convex side moderate, that of the ventral side 

 more slight on account of the considerable swelling throughout the 

 greater part of its length ; polished and shining, without stria? ; 

 aperture slightly oblique, minute, constricted ; apex very small and 

 slender. Length -20 in., breadth, at widest part, -04 in. 



This shell very much resembles Gadulus (Gadus) brevis, Desh., 

 from the Paris basin, and other allied species from the Tertiaries of 

 Europe, and the living C. subfusiformis, Jeff. It is interesting as 

 being the oldest known form of Cadulus, no species having hitherto 

 been recorded from Cretaceous rocks, except Cadidus ( Gadus) pusil- 

 lus, Gabb, from the Cretaceous rocks of California. 



It abounds in the Nucula-bivirgata zone at Folkestone. 



