10 bulletin: museum of comparative zoology, 



of skin passing backward from the side of the head so as to form a valvB. This 

 hollow space is traverse<l by a band of tissue containing the ganglion stellatum 

 and the nerves connected with it. Behind the eye an<l just within the angle of 

 the aperture of the mantle-cavity is a minute papilla, which is presumably the 

 olfactory organ. The rectum, terminates at the base of the funnel in the 

 middle line and emerges from the body wall through the ligamentous attach- 

 ment of the mantle, which is forked to give it passage (Plate 3, Fig. 11). 

 The anal appendages are spatulate. The radula has seven rows of teeth and 

 does not show the arrangement stated by Steenstrup to be characteristic of the 

 genus. According to him each row of the radula differs from those immedi- 

 ately preceding and following it, but in such a way that the pattern repeats 

 itself every five rows. It is quite possible that this character may appear as 

 the animal becomes more mature. The drawing on Plate 4, Fig. 1, will give a 

 better idea of the form and proportions of the teeth than any verbal 



description. 



Dimensions. 



cm. 



Length, total 1-8 



End of body to mantle-margin 0.7 



End of body to eye 10 



Breadth of body lo 



Diameter of largest sucker 0.1 



Right. Left. 



Length of first arm 2.0 2.0 



Length of second arm 1.6 1.6 



Length of third arm 11 11 



Longtli of fourth arm 1.1 11 



Suckers on first arm i 18 18 



Suckers on second arm 1 17 19 



Suckers on third arm ^ 14 12 



Suckers on fourth arm ' 13 12 



On opening the mnntle-cavitij, this is seen to be very short from before back- 

 wards, l)ut very extensive laterally. The mantle is only bound down to the 

 body wall in the median line for a short distance anteriorly (Plate 3, Fig. 11): 

 behind tills it is free, so that there is a communication between the two sides. 

 The gills lie one on either side, quite near the posterior margin of the sac ; each 

 consists of half a dozen lamellae, cresceutic in form, with the concavity directed 

 forwards, and subdivided into numerous tufts. Just at the apex of the gill is 

 attached the ligament which binds down the lateral part of the sijdion, and 

 proceeding outwards from this is a broad fold of skin passing backwards from 

 the heail and furming a valve, when the mantle contracts over it. This fold 

 of skin is large and loo.se, and the cavity, which is arched over by it during 

 expiration, must contain a considerable qiiantity of water, to which must also 



* These numbers arc exclusive of minute evanescent suckers at the tips of the 

 arms. 



