52 
THE VOYAGE OF H.M.S. CHALLENGER. 
II. Order.— NUDIBKANCHIATA HOLOHEPATICA. 
This Order comprises the Dorididae and Doriopsidae, nearly all of which, with the 
exception of one deep-sea form [Bathydoris), are littoral in habit. 
Family Doridida 
Sub-family I. Dorididae Phanerobranehiatae. 
Ohola, n. gen. 
Forma corporis fere ut in Polyceris, sed limbo frontali simplici, recto. Branchia 
pauci-(3-) foliata. Appendices dorsales colosseae, simplices. Tentacula vix ulla. 
Rhinophoria vaginata, clavo perfoliato. 
Lamellae mandibulares fere ut in Polyceris propriis. Eadula fere ut in Polyceris 
propriis, rhachide nuda, pleuris dentibus majoribus hamatis duobus, et dentibus externis 
paucis (2). 
This new genus shows a general agreement with the true Polycera in its outward 
form. The frontal margin, however, has no prolongations, the branchia has only a 
few (3) simple tufts. On the dorsal margin on each side are two huge papillae. The 
rhinophoria are provided with a very marked sheath ; the club is strongly perfoliated ; 
there are no tentacles. — The strong mandibular plates are like those of Polycera 
proper {Polycera quadrilineata) , so also the tongue, which has two powerful lateral 
teeth, and only a few (2) outer teeth. The armature of the penis is like that of 
Polycera. 
Ohola differs, however, from Polycera in having a strong sheath for the rhinophoria, 
in its even frontal margin, the absence of tentacles, and the huge development of the 
dorsal papillae, which give the animal a most remarkable appearance. There is but one 
species known at present. 
Ohola pacifica, n. sp. (PL IX. figs. 9-22). 
Habitat. — Pacific (Arafura Sea). 
Of this form I found a single individual, somewhat altered in shape by pressure, in 
company with Bornella excepta and Janolus australis; it had been preserved in 
picro-sulphuric acid ; the specimen was captured in the Arafura Sea in September 
1874. 
The specimen (fig. 9) was 13 mm. long, 5 mm. broad, and 3 ‘5 mm. high; the length 
of the anterior papillae was 4 mm., of the posterior pair 8-9 mm., the length of the 
