112 THE ROTIFERA. 
In Pterodina the lorica consists of two delicately thin, and nearly flat plates, 
soldered together at their edges; in Pompholyx it is continuous, flask-shaped, and 
without edges. In the former the ventral plate is perforated for the emission of a long, 
wrinkled, toeless foot ; the latter is footless. 
Genus PTERODINA, Ehrenberg. 
GEN. CH. Lorica entire, greatly depressed, of two oval, but nearly circular plates 
soldered together at their edges ; foot wholly retractile, transversely wrinkled, jointless, 
toeless, ending in a ciliated cup. 
The species of this genus differ from each other chiefly in the flexibility, shape and 
adorning of the lorica. In all, the corona consists of two circular lobes, whose ciliary 
wreaths, seen from above, present as perfect an appearance of two revolving wheels as in 
Philodina or Rotifer. The cylindrical foot is encircled by deep constrictions, which 
cease abruptly at some distance from its free end, and is remarkable not only from its 
being the foot of a fixed Rotiferon, but also from its ending in a richly-ciliated hemi- 
spherical cup. There are, too, some other points common to all the species, that deserve 
notice. The salivary (?) glands on the esophagus are very numerous, and the gastric 
glands are of unusual length and shape. They are attached to the junction of the 
cesophagus and stomach by long tapering stalks; and, crossing the lorica transversely, 
are fastened to the dorsal surface by their broad ends. Between these attached ends 
of the gastric glands, and the lowest portion of the head, lie curiously-scalloped folia- 
tions (of a delicately blue-tinted substance) of which it is difficult to say whether they 
are continuous with the gastric glands, or are expansions of the lobed masses investing 
the base of the head, or are something analogous to the floccose ribbons which in so 
many Rotifera surround the lateral canals. They are very conspicuous in P. patina, 
but only faintly visible in P. valvata; and the upper portions of the lateral canals, 
with the attached vibratile tags, lie across them.! The contractile vesicle appears 
to be absent. The longitudinal muscles are coarsely striated, and the two eyes are 
distinct, colourless, transparent spheres resting on ruby pigment. I failed to find any 
dorsal antenna, but the dorso-lateral antenne lie with their rocket-shaped heads close 
to the surface of the lorica near its edge at about one-third of the semi-circumference 
from the top. 
P. patina, Ehrenberg. 
(Pl. XXVI. fig. 11.) 
Pterodina patina . : Ehrenberg, Die Infus. 1838, p. 517, Taf. Ixiv. fig. 4. 
3 4 2 Eckstein, Sieb. w. Koll. Zeits. xxix. 1883, p. 401, Taf. xxvii. fig. 59. 
SP. CH. Lorica inflexible, nearly circular, stippled just within the edge, especially 
on its upper third ; bosses absent from the lorica; gastric glands with broad, lobed ends. 
Lateral foliations very conspicuous. 
This is the common species; but, though no rarity, Miller has rightly described 
it as ‘‘ Animalculum erystallinum, splendore nulli secundum ”’; for it is a lovely crea- 
ture. The dorsal and ventral plates are pressed close together into a glassy shield of 
marvellous thinness. The former is more or less roughened round the edge; and, about 
the level of the mastax, this roughening spreads inwards to some distance. Occasionally, 
too, I have met with specimens in which there were faint traces of bosses, at irregular 
intervals, within the edge; but usually these are absent. A side view enables one to see 
that the ventral plate bulges out along the longitudinal axis, so as to form half of a 
hollow cone, whose broad end is forward, and whose point lies on the ventral surface at 
1 Mr. Gosse differs from me concerning the use of the “gastric glands’’; the presence of the 
vibratile tags; the structure of the foliations; and, generally, concerning the Branchial System in 
Pterodina. His account of this structure will be found in the Appendix. 
