no. 2073. H0L0THURIAN8 FROM NORTHWEST PACIFIC— OHBHIMA. 233 



Family DEXMATID^ ThSel. 



Genus DEIMA Theel. 

 21. DEIMA MOSAICUM, new species. 



Station 4956. Five specimens. 



Station 5084. One specimen. 

 Body elongated oval, 110 mm. long and 40 mm. wide in largest 

 specimen. Mouth and anus situated on ventral surface. Integu- 

 ment thin, very brittle, covered with thin scale-like plates all over, 

 grayish- white in color. Mouth is situated at the center of a circular 

 ridge, 20 mm. in diameter, with papillae of microscopic size on outer 

 margin. Tentacles 18, each provided with 7-10 digits. The odd 

 ambulacrum is naked, except for a pair of small pedicels only 2 

 mm, long, situated immediately anterior to the anus. Pedicels of 

 ventrolateral ambulacra, measuring up to 20 mm. in length and 

 6 mm. across, numbering from 11 to 13 arranged in a row to a side. 

 "Flankenpapilien" are long and cylindrical, up to 80 mm. in length 

 and 7 mm. in diameter at base, 4 or 5 to each row. Another set 

 "eigentliche Ruckenpapillen," form a row on either side of mid- 

 dorsal line, numbering 8 to 10 in each. All over the body, including 

 pedicels and papillae, skin is strengthened with scale-like plates, 

 partly overlapping one another. Those of ventrum measure 0.8-2.0 

 mm. in diameter, those of dorsum 3-4 mm. or more. They are round, 

 with almost entire margin and numerous holes increasing in size 

 toward the center, and rarely attaining the diameter of 180,«. Each 

 scale of dorsum consists of two parallel layers of network, of which 

 the upper one is destitute of spinous processes on its surface. Th^se 

 of ventrum lack the upper layer, but a few tubercles are always found 

 at the central part. The scales of pedicels and papillae are similar to 

 those of ventrum except that the margin is serrated. Around the 

 mouth the plates are very simple and oval, with thorny surface 

 and margin, 0.3-0.5 mm. in diameter, accompanied by delicate, 

 branched rods or plates with a few holes. Pedicel is devoid of end- 

 plate but is supported by rods of various forms, sometimes by per- 

 forated plates. Supporting rods of tentacles have spinose processes. 

 Genital tubes contain in their walls very delicate, thread-like branched 

 rods often congregated to form a complicated apparent anastomosis. 

 Calcareous ring consists of 10 fragile segments. Stone-canal strength- 

 ened by network of deposits; Polian vesicle single. Genital tubes 

 thick and few in number, forming two tufts. • 



While the specimens agree very well with D. blaltei Th6el in the 

 structure of dorsal scales and the number of papillae, they show many 

 other details which are common with D. pacijicum Ludwig. The 



