62 J. S. GARDNER ON THE CRETACEOUS DENTALIID2E. 



This species differs from B. cylindricum, Sby., in its smoother, 

 thinner, and more polished and slender aspect, and from D. glabrum, 

 Geinitz, by its annulation*. 



It is abnndant in the Gault at Folkestone ; and casts, apparently 

 of this species, are met with at Cambridge. It is also common in 

 the cracker rocks at Atherfield, and probably in other Lower-Green- 

 sand rocks. 



I have named it in compliment to Dr. Gwyn Jeffreys, whose 

 researches in the Dentaliidse are universally known, as a slight 

 recognition of much valuable advice and assistance. 



Dentalium acuminatum, sp. nov. Gault. (Plate III. figs. 34-39.) 



Shell very slender and needle-like, cylindrical, thick, nearly 

 straight or very slightly curved ; surface smooth and polished ; 

 sometimes with faint lines of growth ; aperture slightly elliptical ; 

 apex minute, entire. L. '75 in. B. *0416 in. 



This is distinguished from D. cylindricum by its more slender 

 and needle-like aspect, smaller size, and lesser curve. It is one of 

 the smallest and most slender shells of the genus, resembling an 

 Eocene form, D. acicula, Desh., and the recent D. gracile of Jeffrey's. 

 It has hitherto been overlooked, having probably been supposed to 

 be a young form of some other Dentalium. 



Genus Entalis. 

 Entalis Meyeei, sp. nov. Blackdown beds. (Plate III. rig. 40.) 



Shell elliptical, slender, elongated, moderately curved, smooth 

 but not polished, without any lines of growth, as thick in the 

 middle as near the aperture ; apex slender, fissured, the fissure 

 being narrow and extending l the length of the shell ; aperture 

 apparently thin and elliptical, but damaged in the only specimen 

 known. L. -9583 in. B. -1041 in. 



This shell is peculiarly interesting as being the first Dentalium 

 having a slit described from rocks older than the Eocene in Europe. 

 Stoliczka describes a somewhat similar but shorter form, from the 

 Cretaceous rocks of Pondicherry, under the generic name of Fustiaria, 

 ' Palaeontologia Indica,' 1868, vol. ii. p. 445. 



Genus Siphodentalium. 

 Siphodentalium afeine, sp. nov. Gault. (Plate III. figs. 41-44.) 



Shell minute, curved, cylindrical interiorly, subquadrate ex- 

 teriorly. The concave or dorsal side broad, flattened, smooth, 



* In Geinitz's ' Charakteristik der Schichten und Petrefacten des sachsisch- 

 bohmischen Kreidegebirges,' p. 74, the description of D. glabrum is : — " Long, 

 small, slightly bent or straight, quite smooth, with oval section." The fig. 28. 

 pi. xviii. is much coarser than a subsequent figure in the Kieslingswalda(Pl. i. 

 fig. 27), which is slender and has a round section. 





