from Sinai and Egypt. 249 



Three broken specimens, labelled "Eocene," Abu Eoash (1 1379), 

 •HiVe not unlikely to be this species, but sand-polishing has removed 

 all the tubercles, and they are badly crushed. 



? I 3796. Two specimens, probably of the same form, but both 

 diffei'ently crushed. The peripetalous fascicle is distinct, but not 

 the lateral : otherwise they might be L. roachensis. 



2. LiNTHiA OBLONGA (d'Orbiguy), 1854. 



Feriaster oMongm, d'Orbigny, 1854 : Pal. fran9., Terr, cret., vol. vi, p. 275, pi. 900. 

 Linthia oblonga, Feron & Gautliier, 1880: E'ch. foss. Algerie, fasc. 6, p. 79. 

 Linthia ohloiiga, Fourtau, 1899: Eev. E'ch. foss. E'gypte, Mem. Inst, egypt., 



vol. iii, fasc. 8, p. 631. 

 Linthia ohhng a, R. B. Newton, 1904: L. oMonga from Sinai, Geol. Mag. (1904), 



pp. 441-445, PL XV. 



The collection of Spatangoids includes a large series from the 

 ■Cephalopod bed in Wadi Ethal (L 3918), the determination of which 

 has been the most difficult problem in dealing with this collection. 



I have not adopted the easiest course in dealing with them, though 

 that, perhaps, would be the i-ight one. Tliat course would be to 

 ' lump ' most of them in one species and label it Linthia ohlonga 

 (Orb.), and also include therein Hemiaster luynesi, Cott., and some 

 Algerian echinoids described as Hemiaster. 



The specimens from Wadi Ethal show the peripetalous fascicle 

 very clearly ; and in some of them there are obscure traces of the 

 lateral fasciole. The latter specimens can be safely identified as 

 L. ohlonga, as has been done by Mr. R. B. Newton. But the 

 majority of the specimens have no lateral fasciole. In many the 

 tuberculation is so well preserved and the peripetalous fasciole is 

 ■so distinct, that the absence of the lateral fasciole is not due to 

 imperfect preservation. If these specimens are to be included in 

 Linthia, the diagnosis of that genus must be amended to the effect 

 ■that the lateral fasciole may be absent from many specimens of a 

 species. In that case there is no constant difference between Linthia 

 and Hemiaster. 



This conclusion may be the right one, for there is a remarkable 

 parallelism between species of Hemiaster and of Linthia. Thus the 

 Hemiaster luynesi and H^. meslei and H. yseudofourneli may be forms 

 of L. ohlonga without a recognizable lateral fasciole. H. pseiido- 

 Joiirneli would be a somewhat thick variety ; but the following 

 dimensions given by Newton show that there is a considerable 

 variation in the form of L. ohlonga, his second specimen being 

 decidedly narrower in proportion to its width than the others : 



Dimensions : 



1 Cotteau, E'ch. foss. voyage due de Luynes: Bull. Soc. geol. France, ser. ir, 

 vol. sx^-i (1869), p. 535, fig. p. 534. Better figures are given by Lartet: Expbr. 

 geol. Mer Morte (1877), pi. xiv. 



