Some African Rotifers. By J. Murray, 1 



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Habrotrucha pusilla Bryce (2). 

 Synonym: Callidina pusilla. 



Cases with thick walls, of many layers. One case contained 

 two eggs, which measured 90 yu, X 50 /x. 



Hdbrotrocha acorids sp. n. Plate II. figs. 7a-7e. 



Specific Characters. — Size moderate ; anterior trunk strongly con- 

 stricted ; corona large, disks widely separated (for the genus) ; collar 

 prominent, with two large projections at either side of the mouth ; 

 rostrum very short and broad, antenna of moderate length ; teeth, 

 four or five in each jaw ; foot of three segments, no spurs. 



General Description. — Exact dimensions were unfortunately 

 omitted, but it is one of the smaller species, though not among the 

 smallest. The central trunk is expanded when feeding and is 

 closely plicate. The segment immediately in front of it is very 

 strongly constricted, forming a waist, and maintains this shape in 

 all positions. The segment in front of the constricted one is en- 

 larged and of a definite form, which is also maintained in all posi- 

 tions ; it has a projecting annulus at the anterior edge, a constriction 

 below that, and then expands towards the posterior edge. When 

 feeding, the mastax is in this segment. The jaws have a broad 

 border, and have usually four strong teeth and a thinner one 

 on each. 



The head has very distinctive characters. The disks are very 

 large, and their size in relation to the constriction of the anterior 

 trunk produces a curious result. When placed side by side the 

 disks could not pass the constriction, and so they are held one in 

 front of the other, asymmetrically, and this is their usual position 

 in the creeping animal. The sulcus between the disks is about half 

 as wide as a disk and bears normally a large ligule. The folds of 

 skin from the collar end near the middle line in low rounded lobes, 

 which do not project over the "bridge" joining the pedicels. The 

 terminal joint of the rostrum is very short ; it is much broader 

 than long, and is the shortest I know in a Bdelloid. The lamella 1 

 are short and seem quite separate, appearing as two distinct little 

 sharp hooks. The quadrate flaps of skin projecting from the sides 

 of the mouth recall those of Habrotrocha angusta Bryce (3). The 

 length of the antenna is from ^ to § of the diameter of the neck. 

 The rump is pyriform, and shows the two segments. The foot is 

 very short, the first joint larger and tapering, the second very short, 

 cylindrical, without a trace of spurs. The three toes are small but 

 distinct. 



Everything points to H. acornis being a tube-dweller, but it has 

 never been seen in a tube. The constant shape of the trunk, in 

 the feeding attitude, and the size of the constricted segment, even 

 suggest that this is really no other than H. perforata without its 



