380 BULLETIN 100, UNITED STATES NATIONAL MUSEUM 



This is not a deep-water species for it swarms from 36 to 100 meters. 

 It becomes rare in deep waters especially in the more northern locali- 

 ties. It appears sensible to temperature and can hardly exist in 

 cold waters of a temperature inferior to 10° C. Almost all of the 

 Adeonidae moreover live only in the tropical zone. This species 

 prefers sandy bottoms. The little stability of such substrata explain 

 the colonial irregularity and the presence of large zoarial avicularia 

 whose powerful mandibles assure equilibrium and avoid instability. 



The variations of exterior ornament are not occasioned by sur- 

 rounding causes but are principally in relation to the age of the colony. 

 The small oral avicularia certainly in connection with the hydrostatic 

 system are more abundant at the extremity of the fronds; their 

 mandibles are turned toward the top although they are turned toward 

 the base on the frontal avicularium. The physiologic function of 

 the latter is therefore surely different, although unfortunately we do 

 not know what it is. 



The marginal zooecia whose aspect is different from the others are 

 probably gonoecia. Why did they not have a frontal avicularium? 

 In the fenestrate Adeonidae we frequently see such zooecia around 

 the fenestrules but the reason for their occurrence is also obscure. 

 By simple deduction we can only with difficulty reach a knowledge 

 of the biology of these oceanic pygmies. They give up their secrets 

 only on the day when we acclimate them in the aquarium. We note 

 finally that this species does not live in the same localities as Adeonella 

 gibbera. 



Occurrence. — 



D. 5137. Jolo Light, Jolo; 6° 04' 25" N.; 120° 58' 30" E.; 20 



fathoms; S. Sh. 

 D. 5141. Jolo Light, Jolo; 6° 09' N.; 120° 58' E.; 29 fathoms; 



co. S. 

 D. 5144. Jolo Light, Jolo; 6° 05' 50" N.; 121° 02' 15" E.; 19 



fathoms; co. S. 

 D. 5150. Srrun Island, Sulu Archipelago; 5° 23' 20" N.; 120° 



35' 45" E.; 21 fathoms; co. S., Sh. 

 D. 5151. Sirun Island, Sulu Archipelago; 5° 24' 40" N.J 120° 



27' 15" E.; 24 fathoms; co. S., Sh. 

 D. 5192. Jilantaguan Island, off northern Cebu Island; 11° 09' 



15" N.; 123° 50' E.; 32 fathoms; green sand. 

 D. 5235. Nagubat Island, east coast of Mindanao; 9° 43' N.; 



125° 48' 15" E.; 44 fathoms; sft. M. 

 D. 5273. Corregidor Light, China Sea, vicinity of Luzon; 13° 

 58' 45" N.; 120° 21' 35" E.; 114 fathoms; M., Sh., 

 co. S.; 13.5° C. 

 D. 5311. China Sea, vicinity of Hong Kong; 21° 33' N.;. 116° 

 15' E.; 88 fathoms; crs. S., Sh. 



