156 
PACIFIC SCIENCE, Vol. VII, April, 1953 
Euchlanis alata Voronkov, 1912 
PL 2, Figs. 26, 26^, 26^, 27 
1912 Euchlanis alata Voronkov, Mus. Zook 
[St. Petersburg], Ann. 16: 210. 
Dorsal plate: length, 335 ix\ width, 315 \x\ 
frontal width, 160 \x (winged form). Foot, 
110 ji\ toe, 18 jj,. 
The body consists of two plates, dorsal and 
ventral, the dorsal one being much the larger, 
about twice as wide as the ventral. No keel 
is present on the back. In the winged form, 
both sides of the dorsal plate are expanded to 
at least two thirds the length. The posterior 
tip of the wing is pointed, turned slightly 
upward, making the greatest width. The cen- 
tral posterior part gradually becomes low and 
has no notch. At the anterior extremity a large 
V-shaped notch is present. The wingless form 
is elliptical. 
The ventral plate is slightly convex, elon- 
gate elliptical, its posterior border parallel to 
that of the dorsal plate. 
The foot is large, two-jointed, with one 
pair of toes. 
A large central, anterior eye-spot is present. 
Both the winged and the wingless forms 
were collected from the littoral region of Tai- 
taik (1/3). They are 20 per cent larger than the 
form recorded by Myers (1930). According to 
his note, various stages of "wing” develop- 
ment were found in this species in the acid 
waters of Mt. Desert Island, Maine, but the 
forms from Atlantic County, New Jersey, had 
no lateral wing-like processes. At that time, 
this species had been found in only four 
places in the world, i.e., near Moscow, Rus- 
sia, Arc-en Barrois (Haute-Marne), France, 
and the two localities mentioned above. The 
present finding is probably the first record in 
the Far East. 
Euchlanis triquetra Ehrenberg, 1838 
PI. 2, Figs. 28, 28^ 
1838 Euchlanis triquetra Ehrenberg, Infusions- 
thierchen, p. 461. 
Length, 220 /x; width, 240 \x. 
The dorsal plate is larger than the ventral 
plate, is triradiate in cross section, and has a 
median keel. The sides are roundly expanded; 
in lateral view the highest portion is at the 
center, gradually decreasing in height ante- 
riorly and decreasing suddenly near the pos- 
terior end. The ventral plate is slightly con- 
cave, about two thirds as wide as the dorsal 
plate. This species was found in the littoral 
region of Tai-taik {ih). 
Testudinella bidentata (Ternitz, 1892) 
PI. 3, Figs. 34 , l)Aa 
1892 Pterodina bidentata Ternitz, Rotatorien I 
der Umgebung Basels, p. 20. | 
This species is nearly circular in shape. The 
dorsal plate has a convex frontal edge with a 
small central notch. On each side of the hind i 
ji 
portion a small triangular projection is pres- 
ent, the tips of which are 100 micra apart. In 
the ventral plate the frontal edge is concave, | 
but it swells out slightly centrally. A poly- 
gonal foot-opening is situated at the posterior 
extremity. In cross section (Fig. 34^), the 
ventral side is flat, but the dorsal side forms 
a low arc. This species was found in the region 
off the shore of Tai-taik (1/3). In Japan there 
is only a single record from the Koishikawa 
Botanic Garden of Tokyo (T. Kawamura). 
Ploesoma triacanthum (Bergendal, 1892) 
PL 3, Fig. 36 
1892 Gastroschiza triacanthum Bergendal, Univ. 
Lundensis, Acta 28: 1. 
The anterior end of the head is separated 
into three triangular processes of which the 
central one is the longest. In general, this 
portion bends downward as a shield-like head. 
This species was found only in the littoral 
region of Tai-taik (1^). 
Keratella cruciformis (Thompson, 1892) 
var. eichwaldi Levander, 1894 
PL 1, Fig. 14, 15 
1892 Anuraea cruciformis Thompson, Liver- 
pool Biol. Soc., Proc. 6: 77. 
