47 



Living animals: 



Stat. T,6. 7°38'S., 117° 31' E. ±60 spec. 



Stat. ■^j. Saiius 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 Cavolinia longirostris by Pelseneer "). His assertion seems, 

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

 young form. 



Cavolinia lo7igirostris is certainly tlie most common species of Cavolinia in the East- 

 Indian Archipelago. For that reason "■ Hyalaca levigafa" has been caught in very great numbers. 



6. Hyalaca depressa d'Orbigny. 



1825. "■: Plturopns pcllucidiis Eschscholtz, Bericiit über die zoologische Ausbeute wahrend der 

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



1S3Ó. Hyalaca depressa d'Orbigny, Voyage dans l'Amérique meridionale, vol. V, p. iio, 

 pi. VII, figs. 1 1 — 14. 



1850. Clio pellucida {part.} Gray, Catalogue of the Alollusca in the collection of the British 

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



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



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



1853. Cleodora cnrvata 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. II, p. 611. 



Living animals: 



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



Stat. 130. 5° o'N., i25°26'.5E. 5 spec. 



Stat. 144. Damar Island. 3 spec. 



As to the species to which this form must be referred, it is certainly the young stage 

 of Cavolinia injïexa. The genera! 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 exhibit 

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



Anatomical Notes. 



The anatomy of the genus Cavolinia (including the subgenera Diacria 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 anatom)- of Cavolinia. It has been the species Cavolinia Iridentata especially 

 which served most frequently for anatomical and histological researches. 



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



1) Op. 5. c. p. 90. 



2) Chall. Rep. LXVI, p. 28—37. 



