REPORT ON THE PTEROPODA. 55 



type, with common characters of the two groups Thecosomata and Gymnosomata, 

 because these groups are very distinctly separated from one another. 



* Halopsyche gaudichaudl, Souleyet (PI. III. figs. 7-9). 



1852. Euribia, gaudichaudil, Souleyet, Voyage de la Eonite, Zoologie, t. ii. p. 253, pi. siv. 



figs. 1-6. 

 1883. Thecearybia norfolkensis, Lankester, Mollusca, Encycloptedia Britannica, ed. 9, vol. xvi. 



p. 666, fig. 83. 

 1886. Halopsyche gaudichaudil, Boas, Spolia atlantiea, p. 173, pi. viii. fig. 119. 



Body ovate, nearly globose, barrel-shaped, rounded at the posterior extremity. 



Head small and rather short. 



Fins long, wide and truncated at their extremity, of which the margin is sHghtly 

 sinuous. 



Radula. — Formula 1:1:1; the median tooth entirely differs from that of the 

 Thecosomata, and on the contrary much resembles that of Clione ; the lateral teeth are 

 long and narrow and have a wide basal part, as in all the Gymnosomata. 



Colour. — Nearly absent ; the body-wall is translucent and slightly yellowish. 



Length, 4 mm.; very large specimens reach G or 7 mm. (Souleyet). 



Challenger Specimens. — West Pacific locality — Station 170, July 14, 1874; off the 

 Kermadec Islands; lat. 29° 55' S., long. 178° 14' W. 



Australasian locality — Station 201, October 26, 1874; off Mindanao, Philippine 

 Islands ; lat. 7° 3' N., lat. 121° 48' E. (numerous specimens). 



Habitat. — West Pacific Ocean, to long. 174° E.. between lat. 40° N. (Kiel Museum), 

 and lat. 29° S. (Challenger Expedition, Station 170); generally in large shoals. 



Observation. — According to Macdonald 1 this species possesses the curious peculiarity 

 of being ovoviviparous. The larvas are proportionally longer than the adults; they are pos- 

 teriorly a little pointed and thus possess the general form of the larvae of the Gymno- 

 somata (PL III. fig. 9). The two posterior ciliated rings remain visible until a late period. 



Cymbulia norfolhensis, Quoy and Gaimard, 2 must be related to the present genus ; 

 it seems very close to Halopsyche gaudichaudl, from which it only differs (according to 

 the figures of Quoy and Gaimard) by having small tubercles on the wall of the body. 

 Cymbulia norfolhensis was caught near the Norfolk Islands, and measures about 5 mm. in 

 length, but it is not well enough known to definitively decide its systematic position. 



In regard to Euribia hemispherica, Rang 3 and Psyche globulosa, Rang, 4 both from 



1 On the Anatomy of Eurybia gaudichaudl, Trans. Linn. Soc. Lond., voL xxii. p. 246, pi. xliii. fig. 9. 



2 Voyage de decouvertes de r Astrolabe, Zoologie, t. ii. p. 376, pi. xxvii. figs. 31, 32. 



3 Description de deux genres nouveaux appartenant a la classe des Pteropodes, Ann. d. Sci. Nat., ser. 1, t. xii. 

 p. 329, pi. xivB. figs. 9-11. The specimens called Euribia hemispherica in the British Museum are not Pteropods. 



* Description d'un nouveau genre de la classe des Pteropodes, Ann. d. Sci. Nat, s&\ 1, t. v. p. 284, r>l. vii. fie 1. 



