132 THE ROTIFERA. 
ending in fans of imbricated sete, in the conical shape of the body, and in the broad 
truncate corona; but they differ strikingly in the way in which the limbs are set on the 
body : for in Pedalion they are arranged around it parallel to its longitudinal axis, while 
in Hexarthra, as in the Nauplius larva, they radiate from the centre of the ventral surface. 
Nor is this the only difference. Hezxarthra’s limbs are in three graduated pairs, while 
Pedalion’s ventral limb is far longer than any of the others: moreover, Hexarthra lacks 
two long stylate appendages, ciliated at the ends, which are to be found on the posterior 
end of Pedalion’s dorsal surface. 
Genus PEDALION, Hudson. 
GEN. CH. Limbs arranged round the body in pairs, and parallel to its longitudinal 
axis ; two stylate, ciliated appendages on the posterior dorsal surface. 
P. mrrum, Hudson. 
(Pl. XXX: fig. 1.) 
Pedalion mirum . : : Hudson, Mon. Micr. J. vol. vi. 1871, p. 121, pl. xciv.; and p. 215. 
“5 n ° j 53 Quart. J. Micr. Sci. vol. xii. 1872, p. 333, pl. xix. 
a aS : . 5 4D Mon. Micr. J. vol. viii. 1872, p. 209, pl. xxxiii. 
a a 5 : ‘ Lankester, Quart. J. Micr. Sci. vol. xii. 1872, p. 338. 
SP. CH. Ventral limb much the largest; dorsal limb on the median line ; lateral 
limbs in two wnequal dissimilar pairs ; the bases of all the limbs, lying in a transverse 
section dehind the dorsal antenna; their free ends terminating in fans of vmbricated 
seta. 
It was in July 1871 that Thad the good fortune to discover this remarkable Rotiferon 
in a small road-side pond near the head of Nightingale Valley at Clifton. On placing a 
specimen of it under the microscope I for a moment fancied that I had brought home by 
mistake some Entomostracous larva, for its outline, its six limbs ending in fans of 
imbricated sete, and its habit of jerking itself through the water, made it resemble the 
ordinary Nauplius of a Cyclops. However, a brief examination showed it to be a true 
Rotiferon, with a splendid corona and with internal organs much like those of T’riarthra 
longiseta. The external form is extraordinary ; not only has it six well-developed limbs, 
but all these limbs are hollow, communicating with the body cavity, and containing pairs of 
opposing muscles prolonged into their interior. The arrangement of the limbs too is more 
effective for locomotion than that in a Nauplius ; for in Pedalion they are attached in pairs 
to its anterior end, and he parallel to the longitudinal axis of the body, so that their united 
stroke acts at a great mechanical advantage ; but in the Nauplius larva the limbs radiate 
from a spot on the ventral surface; and, in consequence of this inferior method of attach- 
ment, produce a very feeble skip compared with the furious rush of Pedalion. The 
corona is unusually large, and consists of two oval saucer-like lobes, so set as to give 
together a heart-shaped appearance to the head. The ei:liary wreath is double, and 
precisely on the pattern of the Philodinade (PI. C, fig. 8). Between the upper and 
lower wreath is the usual groove along which the food is conducted to the mouth. On 
either side the lower wreath dips down to the buceal orifice, which is prolonged ventrally 
into a great curved lip, fringed with very large cilia. The rather small mastax has two 
identical, and that the differences between my description and Dr. Schmarda’s “ reside principally in 
the incompleteness of the details given by the latter, and are consequently differences of omission 
rather than anything else.’’ It is difficult to understand how it can be an ‘‘ omission’ to describe and 
draw all the six legs as radiating from a spot on the ventral surface, while (on the supposition of the 
identity of the two creatures) there is only one on that surface, and all lie round the body and parallel 
to its length. Neither can it well be an ‘‘ omission’’ or an “incomplete detail’ to say that there are 
two legs of equal size longer than all the others, when there is only one such leg. Indeed, were Dr. 
Scl marda really capable of the gross blunders attributed to him by Mr. Deby, the whole of his observa- 
tions would be worthless. 
