184 
between 200 and 300 fathoms instead of littoral and sub-littoral 
as throughout the remaining portions of its range. A similar 
phénomenon at Rockall has been taken as indicating that that 
ocean ,,landmark" has sunk within  comparatively recent times, 
carrying down its echinoderm fauna with it. But the case in the 
West Indies is susceptible of a more satisfactory explanation. The 
Amazons and Orinoco rivers interpose an insuperable barrier, inso- 
far as the littoral crinoids are concerned, between the Brazilian 
coast and the Antilles. But an adaptable species, provided there 
were a suitable food supply, could surmount this barrier by the 
simple process of gradually increasing the depth of its habitat and 
thus - passing under it, in water of a sufficient depth to insure a 
uniform salinity. Thus it is possible that 7ropiometra carinala 
has extended its range northward from Brazil by passing under 
the fresh water discharged into the sea by the Amazons and Ori- 
mnoco, and, having reached the Antilles, has not yet risen again to 
it normal littoral habitat. A species of Comasteridæ, Nemaster 
lineata, the only other littoral comatulid found in Brazil, agrees 
with Tropiometra carinata in inhabiting deep water in the West 
Indies. 
SPARK afra (Hartlaub). 
Antedon afer Litke g: 
Antedon afra 1890. HellanD. Nachr. Ges. Gåttingen, Mai Hog p. 172, 
Antedon macrodiscus 1895. Hard, Zool. Mag. Tokio, Vol 7, 
Tropiometra afra 1907. A. H. Clark, rr Mise. Coll. Rare Tine); 
Vol. 50, p. 349. . 
Bowen, Queensland. A specimen from the type locality 
of this species is more slender than any of those in the U. 8. 
National Museum collection from Japan; the arms are 190 mm. 
long, and the cirri, which are XXII, 21—25 (usually 24), are 
25 mm. long. Dr. Hartlaub's type had an arm length of 190 mm., 
and cirri XL—L, ca. 30. Judging from these two specimens, it 
would seem that the large and rugged specimens from Japan, the 
macrodiscus of Hara, with their more numerous cirrus joints were 
certainly specifically distinet; but a specimen taken by the United 
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