112 THE EOTIFERA. 



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 PTEEODINA, 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 Eotiferon, 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 oesophagus are very numerous, and the gastric 

 glands are of unusual length and shape. They are attached to the junction of the 

 oesophagus 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 Eotifera 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. 1 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 antennae 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, Ehrcnberg. 

 (PI. XXVI. fig. 11.) 



Pterodina patiiut . . Ehrcnberg, Die In/us. 1838, p. 517, Taf. Ixiv. fig. 4. 



. . Eckstein, Sieb. u. Kull. Zcits. xxxix. 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, Miiller has rightly described 

 it as " Animalculum crystallinum, spleiidore 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. 



