158 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



available does not seem to afford a secure basis for the latter course. 

 The A Ibatross specimens were from the following stations, all in the 

 Sulu Archipelago — one colony from each : 



No. 4. Station D5139 (off Jolo Light, Fob. 14, 1J)08, 20 fathoms, coral sand 



(Cat. No. G033, U.S.N.M.). 

 No. 5. Station D5145 (off Jolo Light, Feb. 15, 1908, 23 fathoms, coral sand 



and shells). Growing on the shell of a small living crab (Cat 



No. 5900, U.S.N.M.). 

 No. 1. Station D5136 (off Jolo Light, Feb. 14, 1908, 22 fathoms, sand and 



shells). 

 No. 3. Station D5174 (off Jolo L : ght. Mar. 5, 1908, 20 fathoms, coarse 



sand) (Cat. No. 5901, U.S.N.M.). 

 No. 17. Station D5555 (off Cabalian Point, Jolo Island, Sept. 18, 1909, 34 



fathoms, co:irse sand) (Cat. No. 599G, U.S.N.M.). 

 No. 2. Station D5150 (off Sirun Island, Feb. 18, 1908, 21 fathoms, coral 



sand and shells). Colony differing from the remaining specimens 



in containing blnish-black pigment in the test (Cat. No. 6032, 



U.S.N.M.). 



Sluiter (1909) described P. dubium from colonies obtained by the 

 Siboga Expedition at Muaras Reef off Borneo, and at Kaniungan 

 Ketjil (reef). As already indicated in the list of synonyms this 

 species may perhaps be Leptoclinum margaritiferce Herdman (1906) 

 from Ceylon, but Herdman's description and figures are not suffi- 

 cientl} 7 complete to settle the question. Another possibility is that 

 it is Eucoelium erubescens Gould, 1856. 



From station D5109 (25.8 miles off Corregidor Light, Jan. 15, 

 190S, 10 fathoms, coral) there is a small colony (No. 19) (Cat. No. 

 5899, U.S.N. M.), apparently closely related to the present species 

 or possibly to be regarded as an abnormal example of it, which has 

 undergone degeneration or has suffered by the oncoming of condi- 

 tions unfavorable to its growth after it had attained a moderate size. 

 It is about 20 mm. in greatest diameter and 4 mm. in thickness; its 

 upper surface has very deep convoluted furrows separated by 

 rounded ridges which contain few spicules and no zooids, and are prac- 

 tically colorless, while the basal part of the colony is densely crowded 

 with spicules giving it a chalky-white color; The spicules are fairly 

 large (0.03 to 0.01 mm. in diameter) and have a spherical form, 

 the numerous blunt points or rays of which they are built up scarcely 

 projecting above the surface of the sphere. Whether or not this 

 condition may have resulted from the absorption of the projecting 

 points of a type of spicule similar to those in the other specimens de- 

 scribed above the writer will not attempt to decide; but it seems not 

 unlikely that if abnormal conditions have affected the colony they 

 may also have influenced the development of the spicules. The zooids 

 measure about 1.2 mm. in length in a considerably contracted state. 

 They are neither numerous nor are they present in all parts of the 

 colony. Their poor preservation prevents the demonstration of 

 many of the important points of their structure, but three orders of 



