530 PROF. C. H. o'DONOGHUE : REPORT ON 
I'Jnnophores. The rhinophores, although considerably smaller than the oral 
tentacles, are very obvious cylindrico-conical structures lying close together 
in the dorsiil region about halfway between the oral tentacles and the 
beginnings o£ the pleuropodia. Their terminal portion takes the form of a 
fairly thin flap folded upon itself so as to produce a deep groove facing 
laterally. 
Gill or Ctenidium. The large gill is crescentic in shape and forms a lobate 
plume. The anterior portion is attached by a wide base along the pallial 
cavity and the posterior end is free. Just the edge of the hinder portion 
protrudes from beneath the mantle. 
Shell. The shell is transparent, very thin and soft, and of a pale horn- 
yellow colour. The concentric lines of growth are clearly visible. That of 
the smaller specimen measures 62 mm. by 41 mm. The shell of the larger 
specimen was considerably larger, but left intact. The largest of the Sowerby 
shells in the British Museum was 96 mm. by 79 mm., but it is very dry and 
shrivelled. 
Labial Armature. The wall at tlie hinder end of the buccal cavity is lined 
by a thin semi-transparent cartilage-like membrane; this takes the form of a 
compressed tube, whose diameter is 9 mm. high and 4 nun. at its widest point 
and about 5 mm. long. This is strengthened by two flat cushion-shaped 
bands, 3"25 mm. wide, of a deep brown colour. They almost touch dorsally, 
but are slightly more widely separated at their ventral ends. Under the 
microscope it will be seen that these bands are composed of an enormous 
number of tiny cylindrical rods with rounded ends, closely packed together to 
form a sort of "pile'' as in velvet. In some works these bands are spoken 
of as "jaws," but this is not a good term, as they cannot be considered as 
either homologous in structure or analogous in function with the jaws of 
Nudibranchs. 
Radula. The radula is very well developed, and in the smaller of the two 
specimens measured 15"5 mm. long by 14-5 mm. wide. The total number of 
rows in the radula was from 83-85. The number of teeth in the various 
rows was as follows : in the first row 5 (?'. e., 2. 1. 2) ; in the tenth row 15 
(i.e., 7. 1. 7); and in the seventeenth row about 119 {i.e., 59. 1. 59). The 
rachidial tooth is large and consists of a basal plate in the form of a trapezium 
with a deep notch in the middle of the anterior edge iind a leaf-shaped blade. 
The blade has a broad median denticle with 3 or 4 lateral spines increasing 
in size towards the base and the two lateral smaller denticles each flanked by 
one or two spines. The bases of the inner pleurals are roughly rhomboidal 
with curved sides. The blade contains two main denticles, of which the 
inner is larger and has 5-6 lateral spines. The outer hiis 3-4 laterals, the 
basal one being larger than the others. The pleurals increase in size towards 
the outside, reaching their maximum more than halfway out. Here they 
are much longer and the two denticles are very large and almost smooth — 
