10 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
of skin passing backward from the side of the head so as to form a valve, This 
hollow space is traversed by a band of tissue containing the ganglion stellatum 
and the nerves connected with it. Behind the eye and 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 « 
better idea of the form and proportions of the teeth than any verbal 
description. 
Dimensions, 
cm, 
length, tota Rv. v. SIC 0, e 
End of body to mantle-margin . » s © s., 07 
LU Ot VOAY iU ey) $5. 0... o DU 
VERCH OL KOL esL ov 4 v ncs. NS 
Diameter ol largest suche < i oea v. 01 
Right. Left. 
LSO mar ie hy s BD 2.0 
Length of second aeneo 23 9 4 n L8 1.6 
Length or tm armo 5.5. Ll L1 
Len po fourier > o e a araa Al 1.1 
Sueker on iras... . 18 18 
Suckers on second átm? o, 5... Y 19 
Bicker on titdarmi, « > v 4. .— d 12 
Suckers on fourth arm? . . . . . , . 18 12 
On opening the mantle-cavity, this is seen to be very short from before back- 
wards, but very extensive laterally. The mantle is only bound down to the 
body wall in the median line for a short distance anteriorly (Plate 8, Fig. 11): 
behind this 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, crescentic in form, with the con cavity 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 siphon, and 
proceeding outwards from this is a broad fold of skin passing backwards from 
the head and forming a valve, when the mantle contracts over it. This fold 
of skin is large and loose, and the cavity, which is arched over by it during 
expiration, must contain a considerable quantity of water, to which must also 
1 These numbers are exclusive of minute evanescent suckers at the tips of the 
arms. 
