240 rEOCEEDINGS OF THE MAXACOLOGICAL SOCIETr. 



specific rank. The colour is a uniform dirty but semitransparent 

 white, with no trace of opaque white lines or spots, though they may 

 have been destroyed by alcohol. 



The hepatic diverticula are yellowish. The general appearance 

 suggests a nearly circular piece of white, branched seaweed. 

 Including the cerata, the largest specimen is 9 mm. long and 8 broad. 

 The largest cerata are 4'5 mm. high and 3 wide at the top. The body 

 is an isosceles triangle, 7 "5 mm. long and 4 "3 broad at the widest part 

 in front, besides the two frontal appendages, one specimen has six 

 papillae behind the rhinophores on each side of the body, and two 

 have five. The genital opening is under the first of these papillae, 

 and the vent under the second. The largest and most elaborately 

 developed papilla is the second or third. Its main trunk is 

 divided into four branches, each of which is subdivided four times, 

 and on the tip of each subdivision are four points, which, however, 

 are not completely developed in all instances. The hepatic 

 ramifications correspond with all these ramifications of the papillae. 

 The other papillae are arranged on much the same plan, but are less 

 complete, and the primary divisions are only two or three. The 

 hindermost papillae are small and rudimentary. The frontal 

 appendages are like the papillae, but simpler ; the main axis is bifid ; 

 next come three or four subdivisions, and then three or four points. 

 Like the papillae, they contain ramifications of the liver. 



The rhinophores are much contracted, and seem to me perfoliate. 

 Bergh gives, as a generic characteristic, rhinophoria simplicia, but in 

 describing JI. fonnosa (Semper's Reisen, Heft vii, p. 311) calls them 

 " stark kreisformig gerunzelt." Really simple rhinophores, however, 

 sometimes simulate perfoliation, when contracted by the preserving 

 fluid. The oral tentacles are large, flat, and curved backwards. The 

 foot is straight in front, with ample but not tentaculifoi'm corners. 

 The side-margins are expanded so that the ventral surface is broader 

 than the back, which is flat. 



The jaws are large, but thin and transparent. The cutting edge 

 bears a line of very irregular denticles, which show some traces of 

 being arranged in two rows. In the single specimen dissected the 

 radula consisted of 62 triseriate rows. The laterals are as depicted 

 in Bergh's plates, consisting of a moderately broad basal part, from 

 which rises a pointed but hardly hooked spine. The central plates 

 are of the horse-shoe shape, with a longish median cusp, and, on each 

 side, three very strong denticles, the first pair of which are nearly as 

 large as the central cusp. 



I have compared with these specimens two others from Plymouth 

 which I believe to represent the typical IT. formosa. They have 

 a general resemblance to Tritonia in shape, and the papillae are of 

 moderate size. They appear to be formed by a process of repeated 

 bifurcation, but, as the secondary branches are close to the primary, 

 the arrangement might be described in some cases as quadrifid. The 

 frontal papillae are similar to those at the sides of the body. 

 The colour is a beautiful transparent white. Along each side runs 

 an opaque white line, with a few opaque white spots, and a similar 



