L6 Transactions of the Society. 



Habrotrocha auriculata sp. n. Plate II. figs. 8a, 8b. 



Specific Characters. — Large ; hyaline or pale yellow ; trunk, 

 with few wide longitudinal folds ; corona, large ; disks separated, 

 the upper lip projecting between them like a little column to the 

 level of the top of the disks ; at the side of eacli disk a sort of ring 

 projecting beyond the pedicels, and broken in the middle ; central 

 seta? on disks ; antenna, short ; teeth, many (ten or more) 

 diminishing; foot, short, of three segments, the first bearing two 

 bosses, one in front of the other; spurs, short, divergent, obtuse, 

 without interspace ; toes very short and thick. 



General Description. — Length, when feeding, 400 //,; width of 

 corona, 100 [i ; collar, 75 yu, ; neck, 60 /x ; trunk, 100 fj, ; tip to tip 

 of spurs, 30 fx. Each disk measures 40 fi, and the interspace 20 fi. 

 It is quite filled in front by the prominent upper lip. The central 

 setae spring from very small papilla?. The collar is prominent. 



The ring-like auricles, from which the species is named, are of 

 the most puzzling nature. They appear to have some relation to 

 the cilia of tbe disks, and were, in fact, at first supposed to be 

 merely optical appearances produced by the cilia, but there is no 

 trace of motion in them. The part of the ring rising from the base 

 of the pedicel, just above the collar, seems to be a solid peg-like 

 process. The upper part, which is separated from it by a minute 

 gap, appears to be of a different nature, very tenuous and trans- 

 parent. It continues a ridge which runs round the dorsal side of 

 the disk. The appearances it presents in lateral and ventral views 

 are not readily reconcilable with the dorsal appearance. There are 

 similar auricles in another species, known in England and not yet 

 described, which have puzzled Mr. Bryce as much as those of this 

 species have puzzled me. The length of the antenna is |- of the 

 neck width. 



The jaws are triangular, and constricted below the widest part. 

 The whole surface is almost covered by the teeth, which begin at 

 the widest part, and diminish in thickness towards the posterior 

 end of the jaw, where they become mere lines. Their number is 

 not easily determined, but ten or more may be counted. The whole 

 trunk is finely stippled. The pellets are yellow. There are two 

 strong skin-folds near the middle line, passing from the central 

 trunk on to the rump. The brain is of moderate size. 



Habrotrocha auriculata is a very distinct species, having no near 

 relatives, except the undescribed British species above referred to, 

 which has not got the columnar upper lip, and differs in many other 

 respects. 



Habitat. — Kikuyu, Brit. E. Africa (A. Allan) ; Katoomba, 

 N.S. Wales (Brit. Antarctic Exped., 1907-9). 



