BRYOZOA OF THE PHILIPPINE REGION 393 



Zooecia \Lz -0.50-0.55 mm. Apertura^ a n=0,1 ° mm " 

 (ovicelled) U2 =0.40 mm. P Ua =0.15 mm. 



Zooecia f£z=0.50 mm. Aperturaj^ 1 ^ 0,18-0 " 20 mm ' 



(special) U2 =0.35 mm. lZa«=0.10mm. 



Variations. — The dimensions of the ovicelled zooecia are rather 

 variable as well as the size of their opercula; the aperture bears also 

 a proximal tongue of such a nature that the water can enter into the 

 compensatrix only through two very small lateral slits. 



In place the operculum of the third zooecial form appears a little 

 like an avicularian mandible but detached; it is a true schizoporid 

 operculum indicating on its proximal sinus the existence of a compen- 

 satrix and of a polypide. We have no anatomical knowledge which 

 will permit us to recognize the function of these curious cellules. 



Affinities. — This curious species differs from Hippaliosina rostrigera 

 Smitt, 1872, in its much smaller operculum and its different dimen- 

 sions. It differs from Hippaliosina depressa Busk, 1892, figured by 

 "Waters, 1889, in its much larger measurements, in its higher ovicell 

 and in its inferiorly rounded operculum. 







C D 



E 

 -Opercula, X85, of Hippaliosina triforma, new 

 species 

 A, B. Ovicelled zooecia. C, D. Ordinary zooecia X 85. E. Special zooecium. 



Biology. — Our specimens were almost all living at the time of 

 dredging; they were in reproduction February 15-18, 1908. The 

 species is found in the Sulu Archipelago at shallow depths. We have 

 found only one poor, dead specimen at 388 meters. The larva fixes 

 itself primarily on dead nullipores. The third zooecial form is per- 

 haps an adaptation to a special form of nutrition. 



This species is very prolific, although the specimens are never 

 abundant. The larvae certainly have a large number of enemies to 

 which they serve as food. 

 Occurrence. — 



D. 5137. Jolo Light, Jolo; G° 04' 25" N.j 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. 5147. Sulade Island, Sulu Archipelago; 5° 41' 40" N.J 120° 



47' 10" E.; 21 fathoms; co. S. Sh. 

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

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



