425 
The arms are seventeen or eighteen in number and about. 95 mm 
long; the cirri are 50 mm long with 60 segments. 
This form differs from Th. rustica in having the proximal edge of 
the IBr; produced into a narrow rim which projects over the radials, 
entirely concealing them; the ends of the basal rays are very prominent 
as high dorsoventrally elongate tubercles which are usually rather longer 
than the dorsoventral length of a cirrus socket; in the interradial angles 
the IBr, are cut away to accomodate the basalrays whereas in Th. rustica 
they are separated from the basal rays by the radials which form a con- 
tinuous band all around the calyx. 
Type Locality. — »Siboga« Station No. 226. 
Thalassometra magna sp. nov. 
This new form is related to Th. gigantea, but is easily distinguished 
from that species by the presence of a strong carination on the IBr,, 
IIBr,, IIIBr, and first brachial, these ossicles being in Th. gigantea 
quite without carination though it occurs on all those immediately follo- 
wing; the cirri are proportionately longer and more slender than those 
of Th. gigantea, and are composed of more numerous segments; the arms 
are also more numerous. It is also related to Th. annandalei but is a 
larger and more robust species with larger and stouter cirri, irregularly 
dentate instead of smooth lateral borders to the proximal ossicles, and 
without the great development of spines on the dorsal surface of the 
proximal ossicles characteristic of annandalei. 
The centrodorsal is conical, the tip truncated, 5,5 mm broad at the 
base and 5 mm long; the dorsal pole is mare flat and is covered 
with fine papillae; it measures about 1,5 mm in diameter; the cirrus 
sockets are in ten columns usually of four, the columns of each radial 
area being in close contact with those of adjacent radial areas exteriorly 
but separated interiorly by a bare slightly concave area which is proxi- 
mally nearly or quite as broad as the adjacent cirrus sockets. | 
The. cirri are XXX—XL, 66—74, 70 mm to 85 mm long; the 
longest cirrus segments are nearly or quite twice as long as broad. 
The ends of the basal rays are visible as dorsoventrally elongate 
tubercles bridging over the very deep but very narrow subradial clefts; 
the radials are very short with a slight rounded median prominence and 
with a few small teeth on the distal margin; the IBr, are short, between 
four and five times as broad as long, broadly V-shaped in a direct lateral 
view; the proximal and distal edges are parallel; both the proximal and 
distal edges are slightly everted; the former bears along its margin a 
few short irregularly placed spines; the latter bears, on either side of 
the median line, about eight regular teeth which begin one third of the 
