IfohtT/pe of Sc({\pe\h\m angustiim. G59 



rather narrow and separated from the intraparictcs by a 

 ridge: the intraparictcs are comparatively wide and form 

 a thin wall on each side of the valve. 



None of the characters shown by this valve of S. angustum 

 seems to justify its separation from the species *S'. ungustatum 

 (Gcinitz, 1813, \'ersteiu. von Kieslingwalda, p. 7, \A. iv. 

 fig. 10), which was based on a single carina from the Pliiner- 

 kalk of Strehlen, Saxony, but better figures of the carina, 

 together with scuta and terga, were later giveu by Geinitz 

 (1875, Palajontogr. Bd. xx. A.bth. ii. p. 202, pi. xxxvii. 

 figs. 14-20). Further, there seems little doubt that 

 S. qundricarinatum (Reuss, 1846, Verst. der IJuhmischen 

 Kreidef. p. 105, pi. xlii. fig. 18 ; 1804, Sitz. d. Akad. d. 

 Wiss. Wien, 13d. xlix. Abth. i. p. 238, pi. ii. fig. 14) is also 

 the same species. ^. quadricarinatum, whicli occurs in the 

 Planer-kalk of Bohemia, was likewise established on a carina. 

 Darwin evidently accepted this as a separate species, mainly 

 because of the truncated base shown in the figure (Reuss, 

 184G, pi. xlii. fig. 18) ; but surely this figure represents 

 merely the apical part of a carina, and the truncated base is 

 where the lower part has been broken away, for the growth- 

 linos indicate that the parietes and iutraparietes are incom- 

 plete at the base. 



It is the later figure of S. quadricarinatum given by Reuss 

 (18G4, pi. ii. fig. 14) that best brings out the agreement both 

 with <S. ungustatum (Geinitz) and S. angustum (Dixon), 

 and, since it is evident that one species only is represented, 

 this must be known as «S'. angustatum (Gcinitz). Valves 

 referable to S. angustatum are known to me from the 

 Cenomanian and Turonian of England, and there is every 

 reason to suppose that S. angustatum is the ancestor of the 

 Senonian S.fossula, Darwin. 



Scalpellum angustum, G. O. Sars (1879, Arcliiv. Math, og 

 Naturv. Christiania, Bd. iv. p. 4G6; olim S. stroemii, C. Heller, 

 1878, Deukschr. k. Akad. Wiss. Wien, Bd. xxxv. p. 39, 

 ]']. iv. figs. 13, 14, non S. strwrnii, M. Sars, 1859, Forhandl. 

 Vidensk-Selsk. Christiania (1858), p. 158), is a recent species 

 that appears to be generally accepted as distinct, and, since 

 its name is preoccupied by S. angustum (Dixon, 1850), it 

 may be re-named *S. sarsi, nora. nov, 



I am indebted to ^Ir. Henry D Roberts, Director of the 

 Brighton Museum, tor the loan of the specimen, and also to 

 Mr. C T A. Gaster for information with regard to the chalk 

 pits in the neighbourhood of Southeram, Lewes. 



