46 



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

 of '^ Clcodora pygmaca' agree with what is fouiid in the form costata oi Cavoliiiia quadridentata, 

 occurring abundantly in the East-Indian Archipelago. 



3. " Pleiiropris longijilis" Troschel. 



1854. Plcuropus longifilis Troschel, Beitrage zur Kenntniss der Pteropoden, Arch. f. Naturgesch., 



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



1855. Hyalaea coinplanata Gegenbaur, Untersuchungen über Pteropoden iind 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 Cavoliiiia tridentata^ as Pelseneer-) pointed out. Like this 

 author, I could tracé, 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 foUowing 

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



4. '^Hyalaea rotundata" Boas. (PI. II, figs. 70 — 71). 



1886. Hyalaea 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., 117° 31' E. 2 spec. 



Stat. 189". 2°22'S., 126° 46' E. I spec. 



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

 resemblance to Cavoliiiia globulosa, as Boas himself affirms. It certainly corresponds with this 

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

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



5. '^Hyalaea Icvigatd' d'Orbigny. (PI. II, figs. 72 — 73). 



1836. Hyalaea levigata d'Orbigny, Voyage dans l'Amérique meridionale, vol. V, p. iio, 



pi. VU, figs. 15 — 19. 

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



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

 1858. PleuropHs laevigatus A. and H. Adams, The Genera of recent Mollusca, vol. II, p. 611. 



1) Op. S.C. p. 88. 



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



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



