370 MR JAMES MURRAY ON A NEW FAMILY 
BDELLOIDA. 
All the Bdelloid Rotifera hitherto known have been included in two families, 
distinguished by different types of corona. The Philodinadee have the corona divided 
into two dises, which bear the primary and secondary wreaths of cilia. The Adinetadee 
have no discs, the corona consisting of a flat surface, furred with short cilia, divided by 
a non-ciliated space in the middle line, which may correspond to the space separating 
the dises in the Philodinadee. 
An animal discovered in Loch Vennachar in 1902, in the course of the work of the 
Lake Survey there, could not be referred to either of the known families. After 
prolonged study, continued for more than two years, it is now preposed to constitute a 
new family for its reception. 
MicropiInaD&, n. fam. 
No corona, the ciliated alimentary tract ceasing at the mouth; jaws intermediate 
between the ramate type of all other Bdelloida and the malleo-ramate type of 
Melicerta. 
The only species at present known is a Philodinoid animal. It resembles the genus 
Philodina in general form, in the rostrum, and in having four toes. The absence of 
corona would not of itself have justified the establishment of a new family. It might 
have been regarded as a degenerate Philodina which had taken to a different mode of 
feeding, and lost its corona from disuse. It was only after the peculiar structure of 
the jaws was understood that it became evident that the definition of the family 
Philadinadze could not be modified to include it. 
As now understood, the new family is seen to differ more from the other two families 
of the order than they do from one another. The Adinetadze differ from the 
Philodinadze only in the form of the corona, and in the partly adnate rostrum, free 
at the tip. They have the same form of jaws and of all other structures. 
The Microdinadze differ from both, not only in the lack of corona, but in the shape of 
the jaws. It comes nearer to the Philodinade in the free rostrum and the number of 
toes. On the other hand, the form of mouth might more readily be derived from that of 
Adineta. In Plate II. are shown heads of Philodinadee (fig. a), Adinetadee (fig. c), 
and Microdinadee (fig. b). They are drawn from the ventral side in order to show the 
similar form of lower lip in all. On the same plate are drawn three pairs of jaws :— 
fig. d shows the ramate jaws of Philodinadee and Adinetadee, fig. e those of Micro- 
dina, fig. f those of Melicerta. It will be seen that the jaws of Microdina differ 
about as much from the ramate as from the malleo-ramate type, and sufliciently 
approach the latter, in the anterior position of the teeth and the less rigid union of the 
various parts, to constitute in some degree a link between the Bdelloida and the Rhizota. 
