46 



Pelseneer ') says, as in the adult form the embryonic shell is always lacking. The dorsal ribs 

 of "" Clcodora pyguiaca' agree with what is found in the form costata oi Cavolinia qiiadridentata^ 

 occurring abundantly in the East-Indian Archipelago. 



3. '^Pleuropus longifilis" Troschel. 



1854. neuropils longifilis Troschel, Beitrage zur Kcniitniss der Pteropoden, Arch. f. Naturgesch., 



Jahrg. XX, p. 208, pi. VIII, figs. 1—3. 



1 85 5. Hyalaea complanata Gegenbaur, Untersuchungen iiber Pteropoden und Heteropoden, 



p. 40, pi. I, fig. I. 

 1886. Hyalaea longifilis Boas, Spolia atlantica, Bidrag til Pteropodernes Morfologi, etc., p. 128, 

 pi. 4, figs. 64—65, pi. 5, fig. 78. 



Living animals: 



Stat. 1 36. Ternate. 2 spec. 



Stat. 220. Pasir Pandjang, West coast of Binongka. i spec. 



This form has been recorded only from the Mediterranean, previous to the Siboga Expedition. 



It is certainly the young stage of Cavolinia tridcnlata, as Pelseneer') pointed out. Like this 

 author, I could trace, out of a certain number of specimens (procured from Naples by Dr. Nierstrasz), 

 all the transitions between the young and the adult stage (PI. II, figs. 36 — 53). In the seventh 

 specimen of this series I observed a penis for the first time, and also a gill, while in the following 

 specimens the gonad, situated more proximally than in the foregoing ones, consisted of lamellae. 



4. '^Hyalaea I'otundata'^ Boas. (PI. II, figs. 70 — 71). 



1886. Hvalacn rotundata Boas, Spolia atlantica, Bidrag til Pteropodernes Morfologi og Syste- 

 matik, etc., p. 129, pi. 4, figs. 59 — 61. 



Living animals: 



Stat. 36. 7° 38' S., ii7°3i'E. 2 spec. 



Stat. 189'. 2°22'S., I26°46'E. i spec. 



The description and figures given by Boas, show clearly that this lorm presents close 

 resemblance to Cavolinia globtilosa, as Boas himself affirms. It certainly corresponds with this 

 species'^). Living animals, belonging to the adult form, have rarely been met with by the 

 Siboga Expedition ; while the young animals were onl)- represented by a few specimens. 



5. ""Hyalaea Icvigatd' d'Orbigny. (PI. II, figs. 72- 



■/oj- 



1836. Hyalaea levigata d'Orbigny, Voyage dans I'Amerique meridionale, vol. V, p. no, 



pl. VII, figs. 15 — 19. 

 1850. Diacria laevigata Gray, Catalogue of the Alollusca in the collection of the British 



Museum, prt. II, Pteropoda, p. 11. 

 185S. Pleuropus laevigatus A. and H. Adams, The Genera of recent Mollusca, vol. II, p. 611. 



i) Op. 5. c. p. 88. 



2) Op. s. c. p. 71, 89. 



3) See Pelseneer, Cliall. Rep. LXV, p. 89 — 90. 



