THE MARINE TURBELLAllIA. 291 



COTYLEA. IV. Family Pericelidae, nov. 



6. Pericelis hyerleyana (Coll.) (PI. XIV. fig. 6, & PI. XV. fig. 15, 16, & 17). 



Typhlolepta hyerleyana. Collingwood, Trans. Linn. Soc. Lond. (2) i. p. 92; Lang, Naples 

 Monogr. p. 616. 



Five specimens fi-om Minikoi. 



Collingwood's description of this species is as follows :—" Length f inch, breadth | inch. 

 Body smooth, thin, the lateral parts very ample and puckered. Upper surface beautifully marbled 

 with light brown rings, including roundish spaces of a whitish colour, smaller rings being between 

 the interstices of the larger; most crowded and darkest in colour along the median line, and 

 more delicate towards the side. Under surface of a pale grey, the dendritic markings in the 

 centre of an opaque white. Its movements were very contorted and it did not exhibit much 

 activity. One specimen from under a piece of coral on Pulo Barundum off the west coast 

 of Borneo." 



In Mr Gardiner's collection are five specimens agreeing with this description so far as 

 it goes, save that three of them are of considerably greater size. They are however provided 

 with tentacles on the anterior margin, and with eyes; but I believe that Dr Collingwood may 

 well have overlooked these owing to the extreme folding of the edge of the body. 



Owing to the fact that this species possesses both eyes and tentacles it must be removed 

 from the genus Typhlolepta. Its characters,, moreover, are such as to distinguish it from all 

 other Cotylea sufficiently to make it the type of a new genus and family'. 



The family Pericelidae may be defined as follows : — " Cotylea with small widely separated 

 tentacles, with a complete series of marginal eyes; penis single; pharynx central; margin of 

 the body excessively folded." Genus Pericelis. 



The nearest ally of this interesting form is, I consider, Anonymihs, the only other Cotylean 

 Polyclad in which there is a complete series of marginal eyes. Pericelis further has the an- 

 terior margin notched in the middle line just as in Anonymus. 



The most striking feature of the species, when viewed with the naked eye, is the extreme 

 folding of the margin of the body. In one of the larger specimens the length of the body 

 along the middle line is 35 mm., and the breadth at its middle about 32 mm., whilst the 'rim' 

 of the body when spread out is not less than 230 mm. in length. In this same specimen the 

 small tentacles lie not less than 9 mm. apart. They are crowded with eyes, and eyes are 

 scattered completely round the margin inwards for a depth of about 5 mm. In the middle of 

 the anterior margin is a well-marked notch or indentation, about 5 mm. behind this in the 

 middle line is the elongated cluster of brain-eyes. ' 



Other measurements are as follows : — mouth opening about 18 mm. behind the anterior 

 margin. The male gonopore lies about 4 mm. behind the mouth. The female gonopore about 

 2-5 mm. behind the male. Sucker 1 mm. behind the female orifice. 



To Collingwood's account of the coloration nothing need be added. I have ventured to 

 give a coloured figure of one of Mr Gardiner's specimens to show the position of the tentacles 

 and brain-eyes. It illustrates too the extraordinary amplification of the lateral parts of the 

 body. 



' The species is evidently a widely distributed one. I have received recently a sixth specimen of it from Mr Gardiner 

 from Kotuma in the Pacific. 



