445 



the dredge was let down at first to a depth of 400 m., but during the haul the depth diminished 

 rapidly to 120 m. and the dredge, when drawn up, was torn. A. iiia ladar ictcs [Yahr.) Henderson 

 var. hptopus de Man, finally, has once been collected at a depth of 289 m., but three times 

 between 10 and 50 m. The fact that the species of Alphcus are indeed shallow-water forms 

 results still more clearly from the following. Of the 63 species and varieties, enumerated above, 

 3 1 have been collected on coralreefs, as is shown by the table. They were captured at low 

 tide in small pools on the reef and between blocks of coral. Of these 31 species 11 were taken 

 exclusively on coralreefs, 2 moreover on shallow banks of LitJiothaiunion^ while the remaining 

 18 were caught also outside the reefs by dredge and trawl, but only A. spongiariim Cout. at 

 a depth exceeding 100 m. 



Twenty nine species were caught on a LitJiothamnion bottom. Of these species 13 were 

 taken also on the reefs. Among the remaining 16 species 7 were collected exclusively on Litho- 

 thamnion^ while 9 were taken on other grounds. How much the reef and the Lithothamnio7i 

 bottom are favourite habitats to these animals, is proved by the table. Some species appear 

 from it to have been taken at 8, 9. 11 and even 12 different reefs and their predilection for 

 a bottom of Lithothaninion is proved by the following. At 83 stations species of Alpheics were 

 taken, only at iS stations i) five or more species were collected. When overlooking these 18 

 stations, one observes that in ten of these localities the bottom was covered exclusively or 

 at least for a part with LitliotJiaiiinioii. 



These creatures apparently find a safe and secure habitat between the ramifications and 

 the projecting parts of the pieces of Lithothaninion, with the colour of which they no doubt 

 more or less agree when alive. The tidal current, which is a condition of vital importance for 

 the Litliothamnion, will, no doubt, supply plenty of food, just as is done also by the tidal 

 current on the reefs. 



i) I leave intentionally three other stations (51,71.213) out of regard, because here dift'erent localities — situated very closely 

 near one another — have been united. 



313 



SIBOGA-EXPEDITIE XXXlXo". , 57 



