C. F. ROUSSELET ON CYRTONIA TUBA. 435 



ventral side ; the eggs are deposited and not carried about ; 

 spiny winter eggs have been observed, and I have Lately seen the 

 male (Fig. 4). It is a small, elongated, cone-shaped creature, 

 with only a slight indication of being humped, and otherwise quite 

 straight, having a simple ciliary wreath, a prominent red eye, 

 dorsal and lateral antennae, a contractile vesicle, and two small toes. 

 The jaws and alimentary canal arc quite absent, the elongated 

 sperm sac filling the whole body cavity. The usual longitudinal 

 muscular bands, which are striated, are present, and the circular 

 bands are more apparent than is generally the case. The two small 

 toes are conical and have the usual foot glands. 



This is a very active and restless little Rotifer, constantly 

 swimming about in the open water, except when it anchors itself 

 to a thread and then spins round and round on its longer axis, like 

 a synchaita. It is a summer form, appearing, as far as has been 

 observed, from June to Angust only, and keeps very well in 

 captivity for some weeks in a small bottle, and better than most 

 Rotifers. 



It is evident from the above description that this animal cannot 

 remain in the genus Notommata, as now constituted ; its affinities 

 are with the Hydatinadte, but it does not fit in any of the genera 

 of this family, and, therefore, a new genus for its reception has to 

 be created. I propose to call it Cyrtonia tuba (from KVprciov, 

 a hunchback). 



The generic and specific characters may be stated as follows : — 

 Body conical, tapering from head to the toes, humped, with three 

 distinct bends. Corona truncate, with three styligerous ridges. 

 Ciliary wreaths encircling the corona, and a sub- square space at 

 right angles to it on the ventral side; foot short, confluent, but 

 forming a slight angle with the trunk ; toes, two. Eye, single, 

 cervical. 



A mounted slide of this Rotifer will be deposited in the Cabinet 

 of the Club to serve as type. 



Size, ylo- to ^V^"-' 0^ ^^^^ ^^'^^^ ^^^"*-' T6oi»- Found from 

 June to August at Staines and Hertford Heath. 



Explanation of Plate XX. 



