462 
PACIFIC SCIENCE, VoL XVIII, October 1964 
KEY TO THE GENERA IN THE FAMILY PSOLIDAE 
1(10). Tentacles 10. 
2(7). Dorsal surface with tube feet. 
3(4). Dorsal deposits include hourglass- 
shaped bodies, but lack cups or bas- 
kets T by onep solus Clark 
4(3). Hourglass-shaped bodies lacking, 
cups or baskets present. 
5(6). Sole sharply set off; dorsal deposits 
conspicuous scales, and small cups. 
Dorsal tube feet may pass through 
some of the scales. Sole deposits 
plates or buttons, usually with an ex- 
ternal layer of small deep cups 
Psolidium Ludwig 
6(5). Sole not sharply set off; dorsal de- 
posits small (up to 0.4 mm), smooth 
perforated plates, and cups. Ventral 
deposits plates (similar to dorsal 
plates), and buttons (no cups) 
Neopsolidium n. gen. 
7(2). Dorsal surface without tube feet. 
8(9). Dorsal surface with imbricating 
scales. Mouth and anus dorsal 
P solus Oken 
9(8). Dorsal surface smooth, deposits spar- 
ingly scattered oval perforated plates, 
sometimes with warty surfaces, of 
average diameter 0.1 mm. Mouth 
terminal, anus subdorsal- 
Pseudopsolus Ludwig 
10(1). Tentacles 15 ..Stolinus Selenka 
Neopsolidium convergens (Herouard) 
Cucumaria convergens Herouard, 1901, p. 30. 
Psolidium convergens Perrier, 1904, p. 15; Per- 
rier, 1905, p. 38, text figs. D-F, pi. 2, figs. 
2-4; Herouard, 1906, p. 12, pi. 1, figs. 7, 8; 
pi. 2, figs. 10-12; Ekman, 1925, p. Ill; 
Deichmann, 1947, p. 336. 
DIAGNOSIS: As for the genus. 
MATERIAL examined: Sta. 50, fragment of 
anterior end; Sta. 52, 2 specimens; Sta. 73, 1 
specimen; Sta. 77, 2 specimens. 
remarks : The material examined agrees well 
in most respects with the excellent descriptions 
and figures given by Perrier ( 1905 ) and Herou- 
ard (1906). The total length ranges between 
18 mm and 22 mm while the juvenile specimen 
is 4 mm in length. Colour in alcohol is dirty 
white to light brown. The tentacles are orange 
to light brown, darker in colour than the rest of 
the body. Tube feet are restricted to the radii 
ventrally, where they are arranged in a double 
row in each radius. Near the extreme anterior 
and posterior ends of the body, the feet decrease 
in numbers and adopt a biserial arrangement. 
Dorsally the feet are scattered over both radii 
and interradii. The mouth and anus are slightly 
upturned. There are about 10 anal teeth or 
papillae. 
Deposits in the dorsal skin are thick per- 
forated plates 0.2-0 .4 mm in length (Fig. 2, 8). 
The plates are closely aggregated together and 
overlain by cups, which are 0.14 mm in di- 
ameter (Fig. 2, 6). The cups are lacking in 
the juvenile specimen. Ventrally the plates are 
slightly more irregular in outline and are not so 
closely crowded together (Fig. 2, 10). Inter- 
mingled with the ventral plates, and more 
numerous than they are irregular perforated but- 
tons (Fig. 2, 9). The tentacles contain perforated 
plates and button-like deposits in great numbers 
(Fig. 2, 7). Some of these deposits are curved 
and carry small knobs. 
This species differs from the others known in 
the region ( Psolidium dorsipes and P. disci- 
formis) in possessing the characteristic small 
dorsal plates, which have warranted erection of 
a new genus to accommodate it. 
distribution: Neopsolidium convergens has 
been taken from the waters about Cape Horn, 
Magellan Straits, Falkland Is., and South Georgia, 
in depths ranging to about 15 m, and seems to 
favour life in the Macrocystis zone, where 
Herouard ( 1901 ) first discovered the species. 
Genus P solus Oken, 1815 
DIAGNOSIS: Tentacles 10. Dorsal surface lack- 
ing tube feet, covered by imbricating scales. Sole 
sharply defined, deposits smooth or knobbed 
plates or buttons. 
type species: P solus phantapus ( Strussen- 
feldt ) . 
REMARKS: This genus now contains over 30 
species, which are spread widely over the Arctic 
and Antarctic regions and in the tropics. P solus 
species are most common in shallow water, but 
some types are known from considerable depths. 
