94 THE ECHINODERMS OF TORRES STRAIT. 
madreporite, where they occur on both sides and on the right-hand side are in 4 consecutive 
groups, with 3 or 4ina group. The larger Zanzibar specimens have no such inferomarginal 
papule. The number and arrangement of subambulacral spines is subject to great indi- 
vidual diversity. In the Zanzibar material, both large and small, the typical arrangement 
is well-marked, but in the Mauritius specimen there are very few plates with 2 distinct 
subequal subambulacral spines, and one might well assert that there is only one series of 
such spines; but the indications of a second series can be made out. 
The geographical distribution of this species is uncertain. I know of no indubitable 
records except those from Mauritius and Zanzibar. 
Tamaria dubiosa. 
Linckia dubiosa Koehler. 1910. Indian Mus. Ast., p. 155, pl. xviii, figs. 10, 11. 
This species is known only from a single small specimen (R =28 mm.) from the Anda- 
man Islands. It does not seem possible to refer it to any previously known species, although 
it seems nearly allied to marmorata. 
Tamaria triseriata. 
Ophidiaster triseriatus Fisher. 1906. Bull. U.S. Fish Comm. for 1903, p. 1080, pl. xxx, fig. 3; pl. xxxi, figs. 7, 7a. 
Two young individuals, taken by the Albatross in 68 to 90 fathoms, off the coast of 
Kauai, Hawaiian Islands, are the only known specimens of this apparently well-marked 
species. 
Tamaria tumescens. 
Ophidiaster tumescens Koehler. 1910. Ast. et Oph. des fles Aru et Kei, p. 281, pl. xvi, figs. 3, 4. 
This very distinct species is known only from one specimen, taken at Sungi Barkai, 
Aru Islands, in 10 fathoms. 
PSEUDOPHIDIASTER. 
H. L. Clark. 1916. Zndeavour Rep., p. 54. 
Genotype: Pseudophidiaster rhysus H. L. Clark, 1916, l. c. Monotypic. 
This remarkable genus is quite different from any other in the family, as it is the only 
one which has become modified by or for life in deep water. Several species of other genera 
live at nearly or quite as great depths, but none of them have been noticeably modified 
in conformity to such a habitat. The reduction of the skeleton in Pseudophidiaster would 
seem to be such a modification. 
Pseudophidiaster rhysus. 
H. L. Clark. 1916. Endeavour Rep., p. 55, pl. xvi, figs. 1, 2. 
Further study of a large dried specimen has brought out the interesting fact, which the 
original description fails to note, that at the base of the ray there is a series of actinal 
poriferous areas between the actinolateral plates as in Hacelia and, as in that genus, the 
areas in this series are twice as numerous as in the abactinal and marginal series. In Pseudo- 
phidiaster this actinal series occurs only in the largest specimens and does not extend far 
beyond the disk. Another peculiarity of the big specimen (R =150 to 160 mm.) is that 
the series of papular areas above the superomarginals is double for a considerable part of 
its length; at the very base of the ray and distally the areas are as usual, but just outside 
of the disk an area is twice as high as wide and constricted at the middle; in the next one 
the two halves are quite separate, but one is above the other; and thereafter they are 
more or less irregular in their position with reference to each other. There are thus in this 
genus, just outside of the disk, 12 series of papular areas. Possibly better preserved material 
would reveal other peculiar features in this very unusual sea-star. It is as yet known only 
from the region south of Australia in 60 to 200 fathoms. 
Se 
