MR. J. W. GREGOHt ON" ARCHJ50PNETJSTE3 ABRUPTUS. 169 



it occurs ma)' mark the first comparatively shallow-water deposit 

 formed on the rising ocean-floor/ This Echinoid, though derived 

 from a hed included in the Oceanic Series, does not itself come 

 from an oceanic Eadiolarian marl, and therefore is in no way opposed 

 to the view of the truly abyssal origin of those deposits. 



EXPLANATION OF PLATE IV. 



Figs. 1, 2, & 3, ArchcBopneustes ahruptus, n. sp. -J nat. size. — Fig. 1. Abactinal 



view ; Fig. 2. Actinal ; Fig. 3. Lateral. 

 Fig. 4. Ambulacral plates fi-oin the anterior zone of the left postero-lateral 



ambulacrum. x4 diam. 

 Fig. 5. Left postero-lateral ambulacrum. Nat. size. 

 Fig. 6. The ]3eristome of Archceopneustes cubensis (Cott.), from a sketch by 



M. Cotteau. 

 Fig. 7. The peristome of Asterostoma excentricum, A.g, (after d'Orbigny). 



^ [Since this paper was read, Messrs. Jukes-Browne and Harrison have 

 microscopically examined the Bissex Hill limestone, and find it to contain 

 fragments of the lower beds; this is a further proof that this limestone was 

 formed during the rise of the deep-sea deposits into shallower water. They 

 therefore propose to exclude this rock from the Oceanic Series. But as the 

 limestone was formed far below the limit of the growth of reef corals, and as 

 the small fauna from this bed appears to be composed of extinct species, 

 whereas those from the base of the coral reefs are all recent, they arc here left 

 in the Oceanic Series. — 23rd Feb., 1892.] 



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