136 DR J. F. GEMMILL AND DR E. T. LEIPER 



found in Planocera insignis in the features wherein these organs differ from the 

 Euryleptid type, i.e. absence of vesicula seminalis and of a separate granule 

 gland (6). 



Nuchenceros appears therefore to exhibit certain characters intermediate between 

 the two great polyclad tribes the Acotylea and the Cotylea. Probably in the end a 

 new Cotylean family will have to be created for its reception ; but meanwhile, until 

 the characters of the genital organs are more definitely determined, we think it best 

 simply to call attention to its close general resemblance to Oligocladus, a member of the 

 family Euryleptidse, notwithstanding the fact that none of the Euryleptidse, and indeed 

 none of the Cotylea hitherto described, possess true nuchal tentacles. 



Eeference is made by LANG (7) to imperfect descriptions by KELAART (8) and 

 COLLINGWOOD (9) of an Acotylean species from Ceylon, called by the former Planaria 

 meleagrina and by the latter Stylochoplana meleagrina, which possesses both marginal 

 and nuchal tentacles. As LANG considers that the nuchal tentacles of polyclads are 

 the more primitive, and the marginal ones are newer formations, he is not surprised 

 that cases should occur in which both kinds are present, but he would naturally expect 

 such cases to be Acotylean. In this connection it is worthy of special note that 

 Nuchenceros has a tentacular group of eyes in addition to the marginal and cerebral 

 groups. 



In any case it is evident that the usually accepted definition (10) of the tribus 

 Cotylea must be widened by the exclusion or modification of the two following phrases, 

 " Ohne Tentakeln oder mit Kandtentakeln," " Ausser den Gehirnhofaugen kommen auf 

 dem Nacken keine anderen Augengruppen (Tentakelaugen der Acotyleen) vor," in 

 order that this tribus may still include Nuchenceros, with its special tentacles and the 

 groups of eyes associated with them. 



TRICLADIDA. 



Three specimens identified as belonging to the species Gunda Ohlini, BERGENDAL,, 

 which has been recorded from the coast of Patagonia (11). 



REFERENCES. 



(1) Fauna u. Flora des Golfes von Neapel, vol. ii. p. 589. 



(2) Ergebnisse der Plankton Expedition, Humboldfc Stiftung. II. Heft f, 1896. 



(3) Fauna u. Flora, etc., vol. ii. p. 585. 



(4) pp. 155-160. 



(5) p. 580, and Atlas Taf., 30. 



(6) pp. 236-7. 



(7) pp. 192, 194, 613. 



(8) Journal of the Ceylon Branch of the Royal Asiatic Society, 1856-8, Colombo, 1858, pp. 134-9. 



(9) Transactions of the Linnxan Society of London, II. Series, vol. i., part 3, 1876. 



(10) Fauna u. Flora, etc., vol. ii. p. 521. 



(11) Zoolog. Anzeiger, vol. xxii. pp. 521-4. 



(ROY. soc. EDIN. TRANS., VOL. XLV., 826.) 



