REPORT ON THE NT7D IB RAN CHIAT A. 
133 
is inserted the strong black-pigmented retractor magnus muscle ; the other thinner retractors 
were similarly pigmented in the upper part. The rhinophorial nerve swells above into 
a small rhinophorial ganglion, which gives off several nerves, forming a network of 
branching fibrils, the plexus gangliosus, the ultimate fibrils of which end in the olfactory 
epithelium at the end of the rhinophore. The walls of the cavity of the rhinophoria 
were provided with some special thin nerves. I did not succeed in finding the otocysts, 1 
owing to the strong pigmentation of the central nervous system. The skin (of the 
back) has an outer cuticle, underlying which is a thin single layer of cylindrical epithelial 
cells, among which were a number of variously-sized unicellular glands, with clear or 
granular contents. The peculiar dorsal eyes were present. 2 
The buccal tube (PI. Y. fig. 3) is strong, 6 '5 mm. long, with a diameter at its hinder end of 
8 mm. ; in the middle line above are attached two lateral retractor muscles (figs. 3, 27), and 
just in front of them, running forwards, are a pair of protractors ; on the underside two 
stronger retractors (fig. 3, c); the interior of the buccal tube has the usual longitudinal folds. 
— The strong bulbus pharyngeus \ PI. IV. fig. 26 ; PI. Y. fig. 3) is about 10 mm. long by 
9'75 mm. in breadth and height; the strong radula-sheath also (PI. IY. fig. 26, a; PI. Y. 
fig. 3, cl) projects backwards about 3 - 5 mm.; the underside of the bulbus is flattened, the 
sides rounded, the upper side sloping at a considerable angle, both in front and behind; in 
front, on the under side, are a considerable number of protractor muscles. On opening the 
bulbus there were seen, on either side above the root of the tongue, a longish palatal plate, 
rounded at one end and more drawn out at the other (fig. 4, b, b), of a pale chitinous-yellow 
colour, and about 3 mm. in length by about 1*4 mm. in breadth. A closer examination 
showed these plates to be made up of a number of irregular borders and raised portions, 
generally prolonged into more or less worn-out teeth (figs. 5, 6) ; this whole chitinous 
'layer was about - 2 mm. high. In the longitudinal and transverse furrows, also between 
these palatal plates here and there, instead of the ordinary cuticle, special similar 
thickenings were found (fig. 5). The fine terminal end of the palatal plates was 
continued as far as the opening of the pharynx (fig. 4). The tongue (PI. Y. fig. 4, a) 
was as usual, broad and strong, with a deep dorsal furrow; on the chitinous yellow radula 
there were forty-eight rows of teeth (counting by the outer edge of the radula), of which 
twenty-three were more or less incomplete, with a good many teeth worn ; on the 
point of the tongue there were traces of two series that had dropped away. Further 
back, within the radula-sheath, there were forty-one developed and four not fully 
developed series ; the total number was thus ninety-three. The total length of the 
1 In a small specimen of Onchidium palaense, S., measuring about 2’5 cm., from the Philippine Sea, I discovered 
the otocysts, visible as white points beneath the lens, in front of and above the pedal ganglia ; their diameter 
was about ‘12 mm., and they contained a large number of round and oval otoconia, measuring about ’007 mm. in 
diameter. 
2 Semper found among all the species of Onchidium which he investigated, only two, Onchidium steindcichneri and 
Onchidium reticulatum, that did not possess dorsal eyes. 
