414 PEKCY SLADEN TRUST EXPEDITION. 



the coloration is uniform, though some specimens are lighter than others and the 

 under side is usually rather lighter than the upper. 



To the naked eye the dorsal surface appears to be smooth, hut under a low power 

 can he seen to he covered with small warts of various sizes, sometimes connected hy an 

 irregular reticulation and with minute pits between them. There is no median ridge 

 and no trace of a branchial opening. The integuments are devoid of spines. The 

 dorsal epidermis is thick and consists of several layers of cells : it is profusely pitted 

 with mucus glands and in many places rises into folds. On the under surface of the 

 mantle and on the foot the epidermis is thin, but the foot is highly glandular. It 

 contains both epidermal glands and subepidermal glands with granular contents and 

 communicating with the exterior by long necks. 



The rhinophores are completely retractile. Their pockets are simple holes without 

 sheaths visible to the naked eye ; but in the sections it can be seen that the margins 

 are slightly raised. As preserved, the pockets are often closed. When retracted the 

 rhinophores often exhibit a few (6-7) strong transverse wrinkles or furrows, and these 

 were also present in the specimen obtained at Hotuma. But they are probably not real 

 perfoliations, since they are absent when the rhinophores are completely exserted. In 

 such cases the outline is even and cylindrical. There are no oral tentacles and nothing 

 which can be called a head. In some specimens, the mouth is a simple orifice above the 

 foot, but in others there is a sort of snout. It would seem, however, that this pro- 

 trusion is due to artificial causes and is not a natural and j^ermanent structure. There 

 are no lamellae on the under side of the mantle as in Fhyllidia, &c., but it is uneven 

 and in some cases presents ridges and bulges probably caused by the hepatic follicles. 

 The foot is large, with ample expanded margins. The anterior margin is straight and 

 not grooved. 



When the internal cavity is opened, the central nervous system is seen lying on the 

 top of the oesophagus and surrounding it. There is no trace of a blood-gland. The 

 cerebro-pleural ganglia are rather large and elliptical ; externally they show no 

 division, but a section indicates that the ganglionic mass is of dual origin and divided 

 internally by a constriction into two nearly equal ellipsoids. The pedal ganglia are also 

 elliptical and lie below and rather behind the cerebro-pleural. The buccal ganglia are 

 rather large, close to the pedal ganglia and also close to one another. No gastro- 

 oesophageal ganglia could be found and no otocysts. The eyes are black and lie near 

 the base of the rhinop)hores on the olfactoi'y ganglia, the optic and olfactory nerves 

 being apparently fused. This arrangement is unusual, but something similar may 

 be seen in Bergh's figure (Malac. Unters. in Semper's Reisen, Heft xv. pi. Ixsi. fig. 17) 

 of the nervous system of Tritonia [Candiella) plebeia, where the optic and olfactory nerves 

 are joined for a considerable distance and separate only in their upper portion. The 

 jiigment layer of the eye lines a cup formed of a few large retinal cells, from which 

 iibres run into the olfactory nerve at the base of its ganglion. 



The jaws are yellowish but not deeply pigmented in any part, moderately convex, 

 not very broad, united at the top by a hinge, and provided with short processes. The 

 edge is armed with a row of very distinct projections with spatulate tips. Near the end 



