246 
XXX, 20 — 2 5 (southeastern South America-, 1080 
Metres) Phrixometra 
e'-' cirri with not more than 20 much elongated segments all of 
which are markedly longer than broad, especially the proximal 
P more than XXV cirri, which have 10 — 20 segments 
(eastern Pacific, including the Seas of Okhotsk 
and Japan, from western Bering Sea to the 
Kermadec Islands and New Zealand, and west- 
ward to between Marion Island and the Crozets; 
southwest of Iceland; 144 — 3178 Metres) . . . Thaumatometra 
f- not more than XV cirri, which have not more than 10 
segments (abysses of the Pacific from west of 
Tasmania to west of Japan; 4680 — 5220 Metres) Bathymetra 
Hathrometra A. H. Clark. 
The following described species are referable to the genus Hathroiiieti-a : 
^ Asterias tenella Retzius, 1783. 
Alecto dentata Say, 1825 (probably a synonym of tenella). 
Alecto sarsii Diiben and Koren, 1846. 
Antedo7i prolixa Sladen, 1881. 
Antedon hystrix P. H. Carpenter, 1884 {= prolixa). 
Antedon exigua P. H. Carpenter, 1888. 
Hathrometra norvegica A. H. Clark, 191 3. 
Trichometra A. H. Clark. 
Key to the Species of the Genus Trichometra. 
a^ Over 40 cirrus segments; cirri XL — LX, 40 — 45, 20 mm. long, the last 
15 — 20 segments about as long as broad; arms 60 mm. to 65 mm. long; 
IBr series and lower brachials narrow, entirely free laterally; rounded ventro- 
lateral processes may be developed on the elements of the IBr series and 
first brachials, but these do not meet across the interradial areas (Hawaiian 
Islands; 248 — 639 Metres) vexator 
a" Less than 35 cirrus segments 
b^ more than 25 (25 — 33; usually 27 — 30) cirrus segments of which those 
beyond the twelfth to twentieth are about as long as broad 
c^ ossicles of the IBr series and first two brachials only slightly convex 
dorsally and sharply and broadly flattened against their neighbors; arms 
45 mm. to 65 mm. long; cirri with 25 — 30 segments, 15 mm. to 22 
mm. long; P^ with 20 — 25 segments, 6 mm. long; P„ with 10 segments. 
