1 66 
Thalassometra A. H. Clark. 
Key to the Species of the Genus Thalassometra. 
a^ Eighth and following branchials with two or three long curved spines near 
the distal edge, which become very prominent in the outer portions of the 
arms; margins of the ossicles of the I Br series and lower brachials fringed 
with very prominent blunt spines: radials, elements of the IBr series and 
first two brachials with a rounded and spinous centre raised above the 
lateral portions; lo arms, 50 mm. long; cirri about XXV, 30 — 35 (Crozet 
Islands; 2926 Metres) bispinosa 
a^ Without two or three long curved spines near the distal edge of the brachials, 
which have more or less overlapping and finely spinous distal edges ; rarely 
the central portion of the laterally compressed outer brachials may be produced 
into a single broad, dorsoventrally flattened median overlapping spine 
b^ not more than 30 cirrus segments; cirrus sockets irregularly placed on 
a hemispherical centrodorsal in one irregular row of 15, and an irregular 
partial second row 
c^ very numerous small spines on the ossicles of the division series and 
arm bases; cirri about XX, 25 — 30; 10 — 12 arms about 50 mm. 
long; IIBr series 4 (3 + 4) (near Ascension Island, south 
Atlantic; 756 Metres) . multispina 
c" dorsal surface of the ossicles of the division series and arm bases with 
very few or no spines 
d^ cirri XX, 25; ossicles of the IBr series and first two brachials with 
sharp straight edges fringed with spines, and a few spines on the 
dorsal surface; brachials smooth, without prominent distal ends; 
segments of P^ with tufts of small spines along the distal border; 
10 arms 30 mm. to 35 mm. long (Kermadec Islands; 11 34 
Metres) echinata 
d" cirri X, 2 1 ; ossicles of the IBr series and first two brachials with 
no spines on the dorsal surface ; brachials with prominent distal 
borders bearing very fine spines ; segments of Pj with a few very 
fine spinules; 10 arms probably about 35 mm. long; (Canary 
Islands; 1330 — 1349 Metres) oiinssa 
b" at least 34 (from 34 to 71) cirrus segments 
c' cirri arranged, more or less regularly, in 15 crowded columns, three 
in each radial area of the centrodorsal ; the radial areas of the centro- 
dorsal are not differentiated 
d' size very large; arms 175 mm. long; ossicles of the IBr series and 
brachials as far as the second syzygy fringed on the pro.vimal and 
