47 



Living animals: 



Stat. T,6. 7°38'S., ii7°3i'E. vh 60 spec. 



Stat. 37. Sailus ketjil, Paternoster Islands. ± 200 spec. 

 Stat. 50. Bay of Badjo, West coast of Flores. 2 spec. 



Stat. 169. Atjatuning, West coast of New-Guinea. 2 spec. 



This form was referred to Cavoliiiia longirosfris by Pelseneer *). His assertion seems, 

 indeed, very admissible. The strong median dorsal rib in the adult, is already distinct in the 

 young form. 



Cavolinia longirosfris is certainly the most common species of Cavolinia in the East- 

 Indian Archipelago. For that reason "■ Hyalaea levigata' has been caught in very great numbers. 



6. Hyalaea depressa d'Orbigny. 



1825. } Plcuropus pcllucid-tis Eschschoitz, Bericht uber die zoologische Ausbeute wahrend der 

 Reise von Cronstadt bis St-Peter und Paul, Oken, Isis, p. 735, pi. V, fig. 2. 



1836. Hyalaea depressa d'Orbigny, Voyage dans TAmerique meridionale, vol. V, p. iio, 

 pi. VII, figs. II — 14. 



1850. Clio pelliicida (part.) Gray, Catalogue of the Mollusca in the collection of the British 

 Museum, prt. II, Pteropoda, p. 14. 



1850. Diacrin depressa Gray, Ibid., p. 11. 



1852. ? Cleodora pleuropus Rang, Hist. nat. d. AIoll. Pter., pi. X, fig. 8. 



1853. Cleodora curvata Huxly, On the Morphology of the Cephalous Mollusca, etc., Phil. 



Trans. 1853, p. 42, pi. IV, figs. 4 — 5. 

 1858. Pleuropus depressus A. and H. Adams, The Genera of Recent Mollusca, vol.11, p. 611. 



Living animals : 



Stat. 36. 7°38'S., 1 17° 31' E. 2 spec. 



Stat. 130. 5° o'N., I25°26'.5 E. 5 spec. 



Stat. 144. Damar Island. 3 spec. 



As to the species to which this form must be referred, it is certainh* the )-oung stage 

 of Cavolinia inflexa. The general form of the shell and the curvature of the posterior portion 

 support this opinion. One of the Siboga-specimens (.Stat. 144) presents very close resemblance 

 to the adult form, especially as regards the anterior part of the shell, in which the lips e.\hibit 

 the same characteristic size as occurs in the form labiata of Cavolinia inflexa. 



Anatomical Notes. 



The anatomy of the genus Cavolinia (including the subgenera Diaeria and Cavolinia 

 (s.str.J) is sufficiently well known to dispense with a fresh description. Indeed, the first knowledge 

 about the organisation of the "Pteropoda" in general, has been obtained for a great deal in 

 studying the anatomy of Cavolinia. It has been the species Cavolinia tridentata especially 

 which served most frequently for anatomical and histological researches. 



It has been pointed out already by the thorough investigations of Pelseneer-), that the 



i) Op. s. c. p. go. 



2) Chall. Rep. LXVI, p. 2S— 37. 



