(J58 y\y. '\\ TI. Williers on (he 



Foss. Lepadidrp, p. 37, pi. i. fis;. 2), included the species in 

 the genus Scii/j/e//tnn, hut. since lie had not the liolotype or 

 other specimens hcfore hiui, had to rely ou Dixon's figure^ 

 uhicli lie reproduced. 



The original of Dixon's Xiphidinm angustiim was not in 

 the Dixon Collection, now in the Geological Department 

 of the British ^luseura, and, in spite of several attempts to 

 trace the specimen, it was not till recently, when ou a casual 

 visit to the Brighton Museum, that I noticed it on exhi- 

 bition there. It was then found that the specimen was 

 mentioned in 11. Willett's Catalogue (1871, Cat. Cret. Foss. 

 Brighton Mus. p. 45, No. 35), with a reference to Dixon's 

 pi. xxviii. fig. 9, together with the locality and horizon, " m.c. 

 [ = Middle Chalk], Southeram, Lewes," which were other- 

 wise unknown. Willett was a keen collector of Chalk 

 Fossils, and several of his specimens were figured by Dixon, 

 although in the present instance Dixon gave neither the 

 locality nor collection. 



There are two large quarries at Southeram — one, 

 Southeram Grey Pit, cut in the Lower Chalk, zones of 

 A. varians and H. subglubosus (Mem. Geol. Surv., Cretaceous 

 Rocks of Gt. Britain, 1903, vol. ii. pp. 61>, 70), and the 

 other, Southeram ]iimekiln Quarr}', cut in the Middle and 

 L'pper Chalk, zones of R. cuvieri to M. cor-anguinum (torn, 

 cit. pp. 401, 402 ; vol. iii. 1904, pp. 46, 48). Judging from 

 the chalk in which the specimen is embedded, and still more 

 from the fact that Willett gives "m.c." [ = Middle Chalk] 

 as the horizon, there can be little doubt that it came from 

 the second quarry, and either from the R. cuvieri or Tere- 

 b rata Una-zone. 



The authorities of the Brighton Museum kindly allowed 

 me to borrow the specimen, and since it agrees in measure- 

 ments with Dixon's figure, and what is more important has 

 the peculiarity that the intraparietes are broken oft" as indi- 

 cated in the figure, there is no doubt that it is the type. 



Darwin ( 1851, p. 38) — relying on the accuracy of J. de C. 

 Sowerby's drawing (Dixon's pi. xxviii. fig. 9), which depicts 

 the lower end of the intraparietes as abruptly and obliquely 

 truncated, and also on the sharply pointed basal margin — 

 believed the species to be new. Examination of the type, 

 however, shows that the abrupt truncation of the intra- 

 parietes is due to the valve being broken across near the 

 base of the intraparietes (see PI. X. fig. 8). The valve is 

 comparatively narrow, the tectum only moderately arched 

 transversely, and on each side of the tectum there is a com- 

 paratively narrow but protuberant ridge; the parietes are 



