9S 
THE VOYAGE OF H.M.S. CHALLENGER. 
strong and slightly coiled, and passed into the much thicker penis, which was about 3 
mm. long (fig. 13,/). The latter (the prseputium) has strong internal, longitudinal folds ; 
the opening of the spermatic duct lies above at the bottom of the cavity. The spermatheca 
was spherical, 8 mm. in diameter, nearly empty. The spermatocyst was sac-shaped, bent, 
3 ‘5 mm. long when extended (PI. II. fig. 12, a), crammed with spermatozoa. The inner half 
of the uterine duct (fig. 12, c) was much thinner than the outer and than the vaginal duct 
(fig. 12, h). The mucous gland was white, showing very fine twistings throughout. The 
albumen gland was brownish-yellow, large, nearly half of it laid bare on the posterior 
side of the genital mass. The cavity of the mucous gland was empty ; the duct showed 
the usual double fold, much higher towards its outer end. 
From immediate comparison with the original specimen of Discodoris morphcea, 1 the 
form described above seems merely to represent a darker variety of the same, with much 
stronger and darker colouring of the dorsal side, and with confluence of the darker 
patches of the lower side of the mantle-border. One point may perhaps throw a doubt on 
the identification of the species, viz., the absence of stronger false median dental plates, of 
stronger thickenings on the rhachis, 2 which were distinctly wanting along the whole 
length of the rhachis in the individual here examined. 
Platydoris, Bergh. 
Doris (L.), d’Orbigny, Moll, des lies Canaries, 1834, p. 38. 
Argus (Bohadsck), Morch. Journ. de Conckyl., sdr. 3, t. iii., 1863, p. 31. 
Platydoris, Bergh, Jahrk. d. deutsck. Malacozool. Gesellsck., iv., 1877, p. 73. 
„ Idem, Malacolog. Untersuch. (in Semper, Reisen im Arckip. d. Philipp. Th. II. 
Bd. ii.), Heft xii., 1877, pp. 495-517, Supplementkeft i., 1880, pp. 57-66. 
Corpus coriaceum, rigidum, applanatum, circumferentia ut plurimum ovali vel 
rotundata, limbo palliali lato ; nothseum minutissime granulatum. Apertura branchialis 
paucilobata, stellata ; tentacula digitiformia ; podarium margine anteriore bilabiatum, labio 
superiore profunde fisso. 
Armatura labialis nulla. Lingua rhachide nuda, pleuris multidentatis, dentibus 
hamatis. — Prostata magna. Penis orbiculis duris hamigeris armatus ; vagina armatura 
simili vel cuticula crassiori instructa. 
This genus was established by me in 1877, and appears to form a very natural 
group. 
These animals are usually of rather large size, roundish or oval, and depressed ; the 
-kin is hard and leathery ; the dorsal surface granular ; the edge of the mantle very large, 
1 The originals of SempeBs collection of Nudibranchiata, mostly given to me ky himself, were handed over by me 
io the collection in the University Museum of Copenhagen (Steenstrup). 
2 Cf. loc. cit., p. 538, Taf. lxL tig. 1, act, aa. 
