394 



BULLETIN 100, UNITED STATES NATIONAL MUSEUM 



D. 5577. Mount Dromedario, north of Tawi Tawi; 5° 20' 36" N.; 

 119° 58' 51" E.; 240 fathoms; crs. S.; 12.4° C. 

 Cotypes.— Cat. Nos. 8200-8202, U.S.N.M. 



Genus TETRAPLARIA Tenison- Woods, 1878 

 (Bigemellaria MacGillivray, 1895, and Arborella Osburn, 1914) 



The ovicell is endozooecial. The apertura is schizoporidan with 

 a more or less broad sinus. The frontal is a tremocyst. The zoarium 

 is articulated; the segments bear 4 longitudinal rows of zooecia ar- 



Fig. 150. — Genus Tetraplaria Tenison-Woods, 1878 



A. Tetraplaria australis Tenison-Woods, 1879. Portion of a zoarium. (After 

 Tenison-Woods, 1878.) 



B. Tetraplaria simplex Robertson, 1921 (not Kirkpatrick, 1888). Segment 

 with one ovicelled zooecium. (After Robertson, 1921.) 



C. D. Tetraplaria gryllus Canu and Bassler. C. Longitudinal section, X20, 

 in a segment showing the endozooecial ovicell. D. Operculum, X85. 



E-G. Tetraplaria {Arborella) dichotoma Osburn, 1914. E. Portion of colony- 

 enlarged, showing mode of branching. F. Operculum. G. Zooecia. (E-G. 

 After Osborn, 1914.) 



ranged back to back, the opposite pairs of two sides alternating at 

 right angles with the other two. 



Genotype. — Tetraplaria australis Tenison-Woods, 1878. 



Range. — Eocene (Priabonian) — Recent. 



In 1920 we were acquainted with this genus only from the figures 

 given by the authors, and we placed it in the Escharellidae according 

 to the form of the aperture, the ovicell not being known. Now the 

 discovery of the endozooecial ovicell obliges us to classify it with the 

 Hippopodinidae. 



