14 BULLETIN 100, UNITED STATES NATIONAL MUSEUM 
Genus HYGROSOMA Mortensen 
HYGROSOMA HOPLACANTHA (Wyville Thomson) 
Phormosoma hoplacantha A. AGAssIz, Challenger Reports, Zoology, vol. 3, pt. 9, 
Hehinoidea, p. 101, pl. 11; pl. 12; pl. 12a, figs. 10-18, 1881. 
Hygrosoma hoplacantha Mortensen, Ingolf Echinoidea, pt. 1, p. 59, 1903; Mono- 
graph of the Echinoidea, vol. 2, p. 208, pl. 18, fig. 1; pl. 19, fig. 1; pl. 20, 
figs, 1, 2; pl. 78, fig. 2, 1985. 
Echinosoma hoplacantha A. AGASSIZ and_ H. L. Crark, Hawaiian and other 
Pacific Echini, Echinothuridae, p. 161, 1909. 
Localities Station 5116; Verde Island passage; Sombrero Island 
bearing N. 69° E., 2.5 miles distant (lat. 13°41’00’’ N., long. 120° 
47’05’’ EF.) ; 366 meters; bottom temperature 10.11° C.; January 20, 
1908. One specimen. 
Station 5123; east coast Mindoro; Malabrigo Light bearing N. 44° 
W., 32.5 miles distant (lat. 13°12’45”" N., long. 121°388’45’’ E.) ; 517 
meters; green mud; February 2, 1908. ‘Two specimens. 
Station 5281; China Sea, in the vicinity of southern Luzon; 
Malavatuan Island (N.) bearing 8S. 84° W., 4.3 miles distant (lat. 
13°52’45’’ N., long. 120°25’00’’ E.) ; 367 meters; bottom temperature 
10.22° C.; dark gray sand; July 18, 1908. Three specimens. 
Station 5282; China Sea in the vicinity of southern Luzon; 
Malavatuan Island (N.) bearing S. 84° W., 6.2 miles distant (lat. 
18°53’00’’ N., long. 120°26’45”” E.) ; 453 meters; bottom temperature 
8.56° C.; dark gray sand; July 18, 1908. Three specimens. 
Station 5283; China Sea, in the vicinity of southern Luzon; 
Malavatuan Island (N.) bearing N. 64° W., 8.75 miles distant (lat. 
13°48’30’’ N., long. 120°28’40’’ E.) ; 512 meters; bottom temperature 
8.22° C.; dark gray sand; July 18, 1908. Four specimens. 
Station 5424; Jolo Sea; Cagayan Island (S.) bearing S. 11° W., 
3.4 miles distant (lat. 9°37’05’’ N., long. 121°12’37’’ E.) ; 622 meters; 
bottom temperature 10.22° C.; coral sand; March 31, 1909. One 
specimen. 
Station 5428; in the vicinity of eastern Palawan; Thirtieth of 
June Island bearing N. 62° W., 19.5 miles distant (lat. 9°13’00” N., 
long. 118°51’15’’ E.); 2,020 meters; gray mud; April 3, 1909. One 
specimen. 
Station 5445; east coast of Luzon; Atalaya Point, Batag Island, 
bearing S. 64° E., 3.6 miles distant (lat. 12°43’05’”” N., long. 125° 
01’00’ E.); 700 meters; bottom temperature 6.83° C.; green mud 
and sand; June 3, 1909. Ten specimens. 
Station 5450; eastern coast of Luzon; East Point, Batan Island, 
bearing S. 36° E., 9.2 miles distant (lat. 13°23’15”" N., long. 124° 
00’30”’ E.); 7384 meters; bottom temperature 5.72° C.; green mud 
and coral; June 4, 1909. One specimen. 
