202 THE PTEROPODA 



especially young specimens of Cavoliuiidae occur at the 

 surface (f. i. the catch of numerous ^Hyalaea depressa'^ 

 around the Spanish coast, while not a single adult 

 Cavolinia inflexa was obtained). The most remarkable 

 fact, however, is the occurring of Peraclis at the sur- 

 face. I know not a single instance of its epiplanctonic 

 existence. Only once (Pelseneer, 1906, p. 151) it was 

 found, at night, at a depth of 30 fathoms, in the gulf 

 of Biscay. In all other cases it has been signalized from 

 depths of 100 fathoms and more. 

 Horizontal distribution. Most striking is the constant pre- 

 dominating of L. trochiformis. in comparison of L. huli- 

 moides, in all the hauls of Mr. Buiteudiik. All other 

 authors regard L. trochiformis as a rather rare species, 

 much less numerous than f. i. L. injlata. — Further the 

 occurrence of L. retroversa, in considerable numbers at 

 the surface, in the gulf of Biscay, is worth to be men- 

 tioned. From the same locality it has been recorded 

 quite recently by Pelseneer (1906, p. 149), but only 

 sparingly and at depths of at least 50 fathoms, with 

 exception of one case at the surface. 



LITERATURE REFERRED TO. 



Boas, J. E. V. Spolia atlantica, Bidrag til Pteropodernes Morfologi 

 og Systematik samt til Kundskaben om deres geo- 

 grafiske üdbredelse, Vidensk. Selsk. Skr., 6. Raekke, 

 naturvidenskabelig og mathematisk, Afd. IV. 1, 1886. 



Locard, A. Expeditions scientifiqiies du Travailleur et du Talis- 



man pendant Ics années 1880, 1881, 1882, 1883. 

 Mollusques testaces, vol. I, pp. 5 — 31, 1897. 



Meisenheimer, J. Wissenscbaftliche Ergebnisse der deutschen Tiefsee- 

 Expedition auf dem Dampfer //Valdivia" 1898—1899. 

 Pteropoda, 1905. 



Pelseneer, P. Ueport on the Pteropoda collected by H. M. S. Chal- 



lenger during the years 1873—76. Prt. I. — The 

 Gymnosomata. Challenger-Expedition, Zoology. Prt. 

 LVIII, 1887. 



Notes from tlie Ley den IMuseum, ^V^ol. XXIX. 



