84 
of P. eburneum. They are attached to the slender spines of a 
specimen of the Echinoid Chætodiadema granulatum taken 15 kms. 
west of Koh Kut (30—1—1900). The largest of these specimens has 
a capitulum about 1 mm. long. They differ from the adult P. eburneum 
in the following points: (1) the capitulum is not-very oblique; (2) the 
peduncle is longer than the capitulum and is covered with rounded 
chitinous scales; (3) the valves are transparent and brittle; (4) the 
cirri are very short. I cannot, however, detect any very definite 
anatomical difference. 
P. eburneum is widely distributed in the Indian and Pacific 
Oceans. 
Dichelaspis tridens (C. W. Aurivillius). 
D. occlusa, Lanchester, Proc. Zool. Soc. London, 1902 (ii), p. 373, pl. 
XXxV, figs, 6, 6a, 6b, 6ec 
D. tridens, Annandale, Mem. Ind. Museum, vol. ii, p. 107, pl. vii, figs. 1, 2. 
Several specimens attached to the carapace of a small crab 
taken near Koh Kong at a depth of between 10 and 15 fms. 
(24—i—1909). 
The geographical range of this species extends from the Phi- 
lippines to the Bay of Bengal. 
Dichelaspis warwickii (Gray). 
A single individual attached to the carapace of a specimen of 
the crab AÅrcana septemspinosa from near Koh Kut (17—20 fms.). 
This species is widely distributed in the Indian Ocean; its 
range extends from the Persian Gulf eastwards to the China Sea. 
Dichelaspis tydemanni, Hoek. 
Hoek, Cirr. Siboga Exp. (Monogr. xxx1 a), p. 24, pl. ii, figs. 3—13 (1907). 
I have little hesitation in identifying with this species a small 
specimen taken off Koh Chuen in 30 fms., although the shape of 
the scutum differs considerably from that of the individual figured 
by Hoek. The lower branch of this valve is so strongly emargi- 
nate that the valve may be said to consist of three branches, and 
