24) H. N. MOSELEY. 



unfortunately was broken during heavy weather and they 

 perished. Several specimens of a beautifully transparent 

 Planarian were obtained at night with the surface net on 

 August 14th, 1873, on the voyage from St. Jago, Cape 

 Verdes, to St. Paul's Rocks in lat. 9° 21' N. long. 18° 25' 

 ^y., and again on Aug. 19th, in lat. 5° 48' N., long. 14° 20' 

 W. The sea oa each occasion was highly phosphorescent, 

 and the towing net was perfectly crammed with various 

 surface animals. Phillirhoe, Salpse, Megalopa, Squilleri- 

 ctheus, Phyllosoma, together with specimens of Cranchia, 

 Halobates and Plagusia. 



The Planarian is certainly very different in structure from 

 Mr. Darwin's Eurylepta Oceanica, though it resembles it 

 closely in habits and mode of life. From Shjlochus pellu- 

 cidus, it differs in the external characters of general outline 

 and distribution of the eyes^ and far more importantly in the 

 structure of the generative organs. 



The present oceanic form is placed in the genus Stylochus 

 on account of the position of the tentacles. In the arrange- 

 ment of the generative organs it approaches Leptoplana. The 

 classification of Planarian s will necessarily undergo great 

 modification when the anatomical structure of a larger number 

 of forms has been accurately investigated. 



Description of Stylochus pelagicus (sp. n., H.N.M.). 



Body flat elliptical, slightly narrower posteriorly, with a 

 sinuous margin. Pellucid white in colour ; mouth central, 

 elliptical multilobate ; a pair of dorsal tentacles ; eyespots 

 disposed in a pair of rings round the bases of the tentacles, 

 and in two pairs of patches in front and behind the nervous 

 ganglia. 



Length 7*5 mm. ; breadth 4*5 mm. 



Free swimming in lat. 9° 21' N., long. 18° 25' W., and 

 in lat. 5° 48' N., long. 14° 20' W. Although the towing 

 net has been constantly in use during the voyage, this free 

 swimming Planarian has only been obtained on tlie two 

 occasions mentioned above, and then only in small numbers. 

 The animals are extremely lively and swim quickly by means 

 of a rapid sinuous motion of the thin lateral margins of the 

 body. They also crawl over objects in the same vi^ay as 

 ordinary shore Planarians, and are also like these in their 

 extreme voracity, fastening immediately on any dead animals 

 placed in the glass with them. 



Anatomy. — The exsertile pharynx is oval in outline, and 

 presents the usual multilobed appearance Avlicn contracted 

 within its sheath, PI. Ill, fig. 9. The opening on the under 

 surface of the body, by which the sheath communicates with 



