HYDATINADA. 9 
a tube, rich in Rotifera, sent me by Mr. Bolton in the autumn of 1884. It had become, 
in the live-box, accidentally entangled in a small mass of tenacious mucus, which 
evidently annoyed it, and from which it made vigorous but ineffectual efforts to become 
free. I have never met with the form since.—P.H.G.] 
Length of body (without styles), about 45 inch. Habitat. A pool near Birmingham 
(PHEG:): 

Family IX. HYDATINAD. 
Corona truncate with styligerous prominences ; ciliary wreath two parallel curves, 
the one marginal fringing the corona and buccal orifice, and the other lying within the 
first, the styligerous prominences being between the two ; trophi malleate ; foot furcate. 
Ehrenberg’s very extensive family of the Hydatinea, under the name of Hydatinade, 
is here restricted to three genera, viz. Hydatina, Notops, and Rhinops. They are all 
alike in their corona, ciliary wreaths, and trophi, but differ from each other in their 
shape, eyes, and foot. 
The head is truncate with a deep cup-like cavity as it were scooped out of it. This 
cavity lies more towards the ventral surface than the dorsal, so that a transverse slice 
would be horseshoe-shaped, the bend of the horseshoe being to the dorsal surface. 
The principal wreath fringes the outer edge of the cup’s wall, and the secondary wreath 
borders the inner; both wreaths are continued down into the buccal orifice, which hes 
just within a deep notch in the wall of the cup on the ventral surface. 
Styligerous prominences rise in the space between the two wreaths, except in the 
case of Rhinops ; and in this genus the dorsal side of the corona bears a thick proboscis, 
around the edges of which the principal wreath is continued. 
In their habits they in the main resemble each other; for all but Rhinops tolerate 
even very dirty water, provided that it contains an abundance of the minute organisms 
on which they feed. 

Genus HYDATINA, Ehrenberg. 
GEN. CH. Body conical, tapering towards the foot; foot short, and confluent with 
the trunk ; eye absent. 
H. senta, Ehrenberg. 
(Pl. XIV. fig. 1.) 
Hydatina senta . : C Ehrenberg, Die Infus. 1838, p. 413, Taf. xlvii. fig. 2. 
a ni 5 i ‘ Cohn, Sieb. wu. Kéll. Zeits. Bd. vii. 1856, p. 436, Taf. xxiii. 
” c 5 : Leydig, Miiller’s Archiv, 1857, p. 404, Taf. xvi. 
“1 - : ; 3 ; Hudson, Mon. Micr. J. vol. ii. 1869, p. 22, pl. xix. 
H. senta is one of the largest of the Rotifera, and its flashing styles, ruddy teeth, and 
yellow stomach, often stuffed with brilliantly green Huglene, make it a charming object 
for dark-field illumination. Its shape is conical, the corona being the base, and the 
toes the apex. When seen, however, from the side (fig. 1b), especially if a little arched, 
the separation of the head and foot from the trunk is distinctly visible. The styligerous 
prominences are semi-globular cushions crowned with long and rapidly vibrating styles, 
set fan-fashion. It is difficult to say how many cushions there are, owing to Hydatina’s 
incessant restlessness ; but there are probably ten or eleven. Two are on the median 
line; one on the dorsal edge, and one between the first and the cavity of the head. The 
rest are arranged round the cayity in a sort of quincunx fashion ; mainly on the dorsal 
half of the corona. The great hollow in the corona is not only ciliated on its edge but 
