392 BULLETIN 100, UNITED STATES NATIONAL MUSEUM 



Affinities. — This new species differs from Hippaliosina triforma in 

 the triangular form of its avicularia. It differs from Hippaliosina 

 rostrigera Smitt, 1872, in the triangular form of the operculum. The 

 avicularia are somewhat variable in their arrangement and in the 

 direction of their beak. When one of the two is aborted, the other is 

 much larger; then it is placed somewhat below the aperture. 



Biology. — Our specimens showed no ovicelled zooecia in February, 

 1908. This species is found in the Sulu Archipelago in shallow 

 waters of about 25° temperature. It lived especially on nullipores, 

 but here it could subsist only on small fragments. It could expand 

 into large multilamellar colonies on bryozoa; we figured a portion of 

 such a colony which had covered the two faces of an Adeonellopsis. 

 It nourishes itself on diatoms and various spicules. 

 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.J 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. 5145. Jolo Light, Jolo; 6° 04' 30" N.; 120° 59' 30" E.; 23 



fathoms; co. S., Sh. 

 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.J 120° 

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

 Cotypes.—C&t. Nos. 8197-8199, U.S.N.M. 



HIPPALIOSINA TRIFORMA, new species 



Plate 54, figs. 5-7 



Description. — The zoarium encrusts nullipores and fragments of 

 shells. There are three kinds of zooecia. The ordinary zooecia are 

 distinct, separated by a furrow, elongated, claviform; the frontal is 

 convex, surrounded by small, scattered, areolar pores, covered by a 

 granular pleurocyst. The apertura is elongated; the rounded rimule 

 is occupied by a peristomial tongue on which is supported the proximal 

 portion of the operculum. The ovicelled zooecia are broader; the 

 endozooecial ovicell is large, transverse, convex, granular like the 

 frontal. There are always two small oral poriform avicularia. The 

 special zooecia are decorated in front by a salient convex border; the 

 apertura is large, mitriform, elongated. 



Measurements . — 



Zooecia \Lz =0.50-0.55 mm. . . J'fta=0.12 mm. 



(ordinary)^ ^ .35 mm. Apertura lZa =0.07 mm. 



