No. X.— PTEROPODA AND HETEROPODA. 



By Dr. J. J. Tesch, Helder, Holland. 



(Plates 12—14.) 



(Communicated by Prof. J. Stanley Gardiner, M.A., F.R.S., F.L.S.) 



Read 21st April, 1910. 



I. PTEROPODA. 



The Pteropoda, collected by the Percy Sladen Trust Expedition in the Indian 

 Ocean, were few in species. The Gymnosomata indeed were not represented. This 

 may be attributed to two principal causes, viz. (1) the region explored lay wholly in 

 warm tropical waters, and did not extend to areas of cooler temperatures, so that a great 

 diversity of forms, as Meisenheimer* has particularly pointed out, could not be expected ; 

 and (2) only few hauls were made in the open sea, the characteristic dwelling-place of the 

 Pteropoda, as the members of the expedition devoted themselves chiefly to exploration in 

 the neighbourhood of reefs. 



The area of the Indian ocean, in which the Sealark worked, was also explored 

 to some degree by the Valdivia Expedition. We are thus enabled to compare the 

 results of the two expeditions. It is a remarkable fact that not only the Gymnosomata 

 Cliono'psis grandis, Notobranchcea valdivia? and Halopsyche gaudichaudi were not caught 

 by the Sealark, but also that Peraclis moluccensis, which was repeatedly found by the 

 German naturalists, did not occur among the spoils, submitted to me, from the same 

 regions. On the other hand I feel justified in describing a species of Desmoptems as new. 



1. ENUMERATION OF THE SPECIES. 

 A. EUTHECOSOMATA. 



Limacinidse. 

 Limacina Cuvier. 

 1. Limacina injtata (d'Orbigny). 

 Stat. P (124f), Q (2), Chagos Archipelago; u (3), v (1), Farquhar. 



* Wissenscha/Uiche Eryebnisse der deutschen Tie/see-Expedition auf dem Dampfer " Valdivia," 1898 — 1899, 

 Pteropoda, 1905. 



t The figures in brackets indicate the number of specimens. A full list of the stations will be found 

 in Trans. Linn. Soc. Ser. 2. Zool. vol. xii. pp. 170-4; they are indicated by letters. 



