152 BULLETIN 100, UNITED STATES NATIONAL MUSEUM 



Measurements. — 



|k = 0.10mm. „ . \Lz = 0.50 mm. 



Apertura-i, nin Zooecium, 



^ {la = 0.10 mm. Its = 0.32 mm. 



. . , . \Lav = 0A0 mm. 

 Avicularium >, ni _ on 



Uav = 0.15-0.20 mm. 



Affinities. — The operculum is bordered by two sclerites very close 



together. The hooks are long, somewhat curved, very thin. This 



species differs from Thalamoporella falcifera Hincks, 1880, in its 



avicularium almost straight and in wider and much smaller opesiules. 



It differs from Thalamoporella indica Hincks, 1880, in its avicularium 



with very pointed beak, in its smaller opesiules and in the presence 



of two oral tuberosities. 



Biology. — The larvae had become affixed early in February, 1908. 



Our observations and figures accord perfectly with those of Harmer, 



1926. 



Occurrence. — 



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



fathoms; co. S. 



D. 5151. Sirun Island, Tawi Tawi Group; 5° 24' 40" N.; 120° 



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



Plesioty pes— -Cat. No. 7956, U.S.N.M. 



Geographic distribution. — Pacific (Malay region): N. Ubian, Sulu 



Archipelago, 16-23 meters; west of north end of New Guinea, 32 



meters; Torres Strait (Harmer). 



THALAMOPORELLA LINEARIS, new species 



Plate 16, figs. 7, S 



Description. — The zoarium encrusts shells; it is formed of a linear 

 series of zooecia branching dichotomously. The zooecia are large, 

 much elongated, elliptical, little swollen; the mural rim is very thin, 

 scarcely salient, little visible; the cryptocyst is large, convex, smooth; 

 the opesiules are large, crescent shaped, denticulated. The apertura 

 is orbicular; the peristome is thin, sharp, little salient. The ances- 

 trula is a smaller zooecium. 



Measurements. — 



. \ha = 0.20-0.25 mm. „ . \Lz = 0.85-0.90 mm. 



Apertura^, n on Zooecia, _ 



* lZa = 0.20 mm. \lz = 0.55-0.60 mm. 



Structure. — The operculum is bordered with a double sclerite; the 



interior sclerite is thicker; there are two small lateral expansions 



at the level of articulation. It is attached to the ectocyst. Except 



for accidental disarrangement the primoserial zooecia are adjacent 



by their base and arranged in different axes. The ancestrular 



zooecia are on the contrary placed in the same longitudinal axis. 



One branch never cuts across another, a phenomenon which has been 



found also in Stomatopora. 



