84 Proceedings of the Royal Society 
Dorsal lamina represented by a series of large langnets placed 
close together. 
Tentacles much branched, of various sizes, some being very large. 
Olfactory tubercle small but distinct, crescentic in shape, with 
the opening on the left side ; both horns rolled inwards. 
Viscera . — Wall of stomach remarkably folded. Genital masses 
about twelve in number, united in pairs and placed on the inner 
side of the mantle on both sides of the endostyle, the majority 
being on the right side. 
Two specimens from Station 241 (Pacific Ocean, east of Japan) ; 
2300 fathoms. 
Cideolus wyville-thomsoni, n. sp. 
External appearance. — Shape of the body irregularly pyriform or 
wedge-shaped, the anterior end being narrow, while the posterior 
is broad and blunt ; dorsal and ventral edges sloping irregularly 
from the broad posterior end to the narrow anterior end, where the 
stalk is attached. Stalk thin, not long, wiry, running a slight way 
along the ventral edge from its point of attachment, turned towards 
the branchial aperture. Branchial aperture a little dorsal to the 
anterior end, being behind the stalk, directed anteriorly and a little 
dorsally ; atrial aperture in the centre of the posterior end, directed 
posteriorly. Surface irregular, deeply seamed and raised between 
the seams into eminences, capped with slight papillae. Colour 
pale slaty grey. Length of body, 5 cm. ; breadth, 4 cm. ; thickness 
(lateral), 3 - 5 cm. ; length of stalk, 10*5 cm. 
Test cartilaginous, thick but soft, not flexible. 
Mantle thin ; muscle bands strong, but rather distant. 
Branchial sac with six folds on each side, diminishing in size 
from the dorsal to the ventral edge, those next the endostyle being 
very slight. Transverse vessels of three sizes placed in the follow- 
ing manner : — a large one, three small ones, a middle-sized one, 
three small ones, and then a large one ; thus, any two large ones 
are separated by a middle-sized one and six small ones. Meshes 
small, transversely elongated. Spicules smaller and not so much 
branched as in Cideolus murrayi , but more numerous. 
Dorsal lamina separated by a series of close-set large languets. 
