REPORT OH THE NTTDIBRANCHIATA. 
99 
the branchial aperture few lobed and stellate ; the tentacles finger-shaped ; the anterior 
margin of the foot bilobed, the upper lip cleft in the middle. — The labial disk is 
unarmed. The radula has a naked rhachis and a large number of liook-shaped lateral 
teeth. The prgeputium is armed with rows of hard flat disks, each bearing a hook ; the 
vagina has a similar armature, or at least a strongly developed cuticle ; the prostate is 
large. 
Platydoris is not unlike Asteronotas, which differs, however, in being softer and 
smoother, and in possessing an unarmed penis and vagina, and a special dart and gland. 
Hoplodoris 1 comes near Platydoris, but differs in being softer, in the armature of the 
labial disk, and in possessing a dart like IIopl odoris. Piety odoris agrees with Platydoris 
in the hardness of its outer skin, and in the unarmed labial disk, but differs in the smooth- 
ness of the dorsal surface, and in the unarmed condition of the penis; it has no dart. 2 
The genus is confined to the tropical seas. Not much is known about its habits, 
except that its movements are lethargic and slow. Quoy and Gaimard observed the 
copulation of Platydoris scabra, and the throwing off of pieces of the mantle in other 
species. 3 
The following list contains all the known or mentioned “ species ” : — 
1. Platydoris argo (Linne). 
Mediterranean. 
2. Platydoris philippi, Bergh. 
Mediterranean. 
3. Platydoris angustipes (Morch). 
West Indies. 
4. Platydoris eurychlamys, Bergh. 
1 Doris solea, Cuvier. 
Philippine Sea. 
5. Platydoris arrogans, Bergh. 
Philippine Sea. 
6. Platydoris striata (Kelaart). 
Indian Ocean. 
7. Platydoris ellioti (Alder and Hancock). 
Indian Ocean. 
1 R. Bergh, Malacolog., Untersuch., loc.cit., Supplementheft i., 1880, pp. 51-55. 
2 R. Bergh, loc. cit., pp. 75-78. 
3 A similar phenomenon has been described in species of the genera Discodoris and Peltodoris. 
