290 Br. R. L. Sherlock — Foraminifera of Speeton Clay. 



cells. Two varieties exist, microspheric and megalospheric forms 

 respectively (PI. XIX, Figs. \bc, d). The dimorphic condition of the 

 allied P. partschiana, d'Orb. [Hoialia pleurostomata, Schlumb.), was 

 noted by Schlumberger (" Sur le Biloctdina depressa, d'Orb., au point 

 de vu du diraorphisme des Foraniinif eras " : Assoc. Frangaise, Rouen, 

 1883 (1884), p. 526), who merely states that there is a great difference 

 in the size of the initial cell in the two varieties of that species. In 

 P. caracolla the initial cell in a microspheric shell has a diameter of 

 about '0088 mm., and in a megalospheric shell a diameter of -055 mm., 

 or about 6*25 times as much. 



Certain specimens show an approach to P. reticulata (Reuss), but 

 have not been separated from P. caracolla. 



The depth at which P. caracolla lived is not known, as the species 

 is extinct; but the strongly limbate group of Pulvinulin(B to which 

 it belongs are now found at depths of from 70-1,000 fathoms (Brady, 

 Chall.Rep.). 



Horizon. — B base h, B base c, C2, Cg, Cy, Dg (base), D2 (top), Dg. 

 Very abundant. 



Puhinulina lam/plugJii, sp. nov. (PL XIX, Fig. 16.) 



Description. — Test free, rotaliform, obtusely conical, the inferior 

 surface nearly flat, the periphery acute and very slightly lobulated. 

 Three convolutions, with usually five segments in the last. Sutures 

 limbate, except the last. The cells, as viewed from the superior 

 surface, are plano-convex, or very slightly concavo-convex in outline. 

 The species belongs to the P. elegans group and is isomorphous with 

 Discorhina isalelleana (d'Orb.). The nearest ally is P. carpenteri, 

 Reuss. Width of test at widest about '42 mm. ('Ol? in.). The depth 

 from apex to base is about '22 mm. ("0085 in.). I have named the 

 species after Mr. G. W. Lamplugh, F.R.S., "whose name will always 

 be associated with the Speeton Clay. 



Horizon. — Found in B base c, C2, and C3. One specimen in B base c, 

 common in C2 and Cg. 



General Concltisions. 



In all forty-four species (one of which has been only generically 

 named, and will not, therefore, be further considered) and one variety 

 have been recognized in the Speeton Clay. Of these, two species and 

 the variety are new. Of the remaining forty-one species, twenty- 

 three are still living, and seventeen of these are known from Jurassic 

 or older deposits, one from the Lower Greensand, one from the Gault, 

 and four from Tertiary deposits. Of the eighteen extinct species 

 previously known, two range from the Jurassic to the Gault, but 

 sixteen have only been found in Cretaceous strata. Including with 

 these the two new species, it appears that eighteen, or 42 per cent, 

 are Cretaceous only. Further, five species, or 11 per cent of the 

 whole, are, so far as is known, confined to Lower Cretaceous beds. 



Many species are represented by a single or very few specimens. 

 If we consider not only the number of species but the number of 

 individuals, it appears tliat the Speeton Clay of Yorkshire is 

 characterized by the great abundance of Puhinulina caracolla 

 (Roemer), which is so plentiful that individuals of this species 



