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XXIX. — Turbellaria of the Scottish National Antarctic Expedition. By Dr J. F. 

 Gemmill and Dr R. T. Leiper.* Communicated by Sir John Murray, K.C.B. 



(With a Plate.) 



(Read March 5, 1906. Issued separately August 7, 1907.) 



There were seven Turbellaria in the material handed to us by Mr W. S. Bruce, all 

 obtained in April 1903 from Scotia Bay, South Orkney Islands (9-10 fms., Station 325, 

 lat. 60° 44/ S., long. 44° 51' W.). Their occurrence is interesting, as, although Studer 

 [Ueber Seethiere aus dem Antarktischen Meere, 1876) mentions, without adequately 

 describing it, a Eurylepta from Kerguelen Island, there are no definite records, so far as 

 we have been able to ascertain, of Turbellarian species from nearer the Antarctic than 

 the coasts of South America. 



POLYCLADA. 



Tribus Cotylea. Fam. Euryleptidw. Genus A ceros (1). Aceros stylostomoides,n. sp. 



(Plate figs. 1 and 2.) 



Specific Diagnosis. — An Aceros with mouth and male opening extremely closely 

 approximated ; with dorsal pore connecting the hinder part of the main gut with the 

 dorsal surface ; with about fifteen eyes on either side in the brain groups, and eight to 

 nine in the marginal groups. 



The two examples of this species are much curled. They measure 3-4 mm. in 

 length and "9 mm. in greatest thickness, and they are of a warm brown tint, mottled on 

 the dorsal surface by a coarse, darkly pigmented network, the strands of which arise 

 from a longitudinal band on either side of the middle line. 



As the specimens differ in the relative degree of contraction of certain parts (notably 

 the pharynx), they will be distinguished hereafter, when necessary, as specimen (a) and 

 specimen (b). 



Body Wall. — The musculature is strong ventrally, especially in the region of the 

 sucker, but over the dorsum it is weak, being channelled by the coloured network 

 mentioned above. This appears to be formed by spaces within and immediately beneath 

 the muscular layer, containing numerous minute round particles of brownish black 

 pigment. The sucker lies a little behind the middle of the body. In specimen (a) its 

 centre is near the junction of the third and fourth body fifths, and in specimen (6) 

 slightly further forward. It is of large size and slightly elevated. 



Digestive System. — The mouth (external opening of pharyngeal sac) is situated at 

 the commencement of the second body fifth. In specimen (a) the pharynx measures 

 less than a fifth of the body length, its own length being about a fifth greater than its 



*■ This paper was prepared in part during Dr Leiper's tenure of a Carnegie Research Scholarship. 

 TRANS. ROY. SOC. EDIN., VOL. XLV. PART III. (NO. 29). 118 



