28 BULLETIN 100, UNITED STATES NATIONAL MUSEUM 
Order AULODONTA 
Family ASPIDODIADEMATIDAE 
Genus PLESIODIADEMA Pomel 
PLESIODIADEMA INDICUM (Déderlein) 
Dermatodiadema indicum D6DERLEIN, Zool. Anz., vol. 28, p. 21, 1901.—pE MEIJERE, 
Siboga Hchinoidea, p. 46, pl. 38, fig. 23, 1904.—DODERLEIN, Wiss. Ergebn. 
Tiefsee-Exped., vol. 5, Lief, 2, p. 158, pl. 20, figs. 2, 3; pl. 41, fig. 2, 1906.— 
Mortensen, Vid. Medd. Dansk Naturh. Foren., vol. 76, p. 65, fig. 2, 1928. 
Localities —Station 5440; west coast of Luzon; San Fernando 
Point Light bearing N. 82° E., 23.1 miles distant (lat. 16°33’52”’ N., 
long. 119°52’54”’ E.) ; 314 meters; bottom temperature 11.78° C.; fine 
gray sand and globigerinae; May 10, 1909. One small specimen. 
Station 5625; between Gillolo and Kayoa Islands; Kayoa Island 
(SE.) bearing S. 3° W., 6 miles distant (lat. 0°07’00’’ N., long 
127°28’00’’ KE.) ; 240 meters; gray mud and fine sand; November 29, 
1909. Seven specimens. 
Remarks.—The specimens from station 5625 are all of about the 
same size, about 30-32 mm. in horizontal diameter. None of them 
have any of the primary spines intact. In one of them the fairly well 
preserved aboral spines, which form the usual erect tuft, are of a 
light purplish color. 
The specimen from station 5440 is only about 11 mm. in horizontal 
diameter and is by far the youngest specimen known. It already has 
spines on the buccal plates, and the genital pores have just appeared. 
In some of the large specimens from station 5625 that I opened 
I found a good number of a very peculiar ertoparasitic halacarid, 
which has recently been described by Dr. Karl Viets ® under the name 
Enterohalacarus minutipalpus—the only case as yet known of a truly 
entoparasitic halacarid. 
These specimens likewise disclosed the interesting fact that this 
deep-sea species prefers a vegetarian diet, the intestine being full of 
small bits of plants, apparently land plants, carried out to sea, where 
they have sunk to the bottom to form the staple food of deep-sea 
echinoids, 
PLESIODIADEMA AMPHIGYMNUM (de Meijere) 
Dermatodiadema amphigymnum DE MEIWERE, Siboga Echinoidea, p. 47, pl. 14, figs. 
195-202, 1904. 
Locality,—Station 5654; Gulf of Boni, Celebes; Cape Tabako bear- 
ing N. 17° E., 21.5 miles distant (lat. 3°42’00’’ S., long. 120°45’50’” 
E.); 1,471 meters; December 18, 1909. One specimen. 
® Zeitschr. fiir Parasitenk., vol. 10, pt. 2, pp. 210-216, 1938. 
