466 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 14 



Genus TETRAPLARIA Tenison-Woods, 1878 



Zoarium with an encrusting base, from which rise erect, articulated 

 branches with corneous joints, branching dichotomously. Genotype, 

 T. australis Tenison-Woods, 1878:61. 



The zoarium of this genus has a small encrusting base, hitherto 

 unknown. In the species discussed below, the one base consists of about 

 20 zooecia, only 6 of which are functional in nutrition, the others being 

 closed. This base measures about 3 mm long by 2 mm wide; from 

 it there arise 5 erect branches, each from a small interzooecial keno- 

 zooecium, the joint being similar in size and form to those between the 

 internodes. Each internode begins with 2 zooecia arranged back to back, 

 which arise from a kenozooecium between the terminal zooecia of the 

 internode. 



Tetraplaria veleroae new species 

 Plate 57, figs. 1-3 



Zoarium with a small encrusting base and erect, jointed branches. 

 The functional zooecia of the base measure 0.40 to 0.50 mm long by 

 0.26 mm wide. The closed heterozooecia are very variable in form and 

 size. The ancestrula is similar to the later zooecia, but is considerably 

 smaller. 



The zooecia of the erect branches are arranged in alternating pairs, 

 back to back, 2 to 4 pairs in a series, in the internodes ; about 0.70 mm 

 long by 0.55 mm wide, elliptical with a narrowed proximal end, distinct 

 with shallow grooves and narrow raised lines. The frontal is a granular 

 tremocyst with numerous small pores, moderately inflated and elevated 

 toward the distal end. The aperture is nearly round, 0.16 mm in each 

 dimension, with a broad shallow sinus between the small cardelles. The 

 aperture of the fertile zooecia is much broader, 0.20 mm. 



The endozooecial ovicell is exposed at the surface, broad and short, 

 0.40 mm wide by 0.18 mm long, rough and perforated like the front 

 but with a thin collar around the aperture, which is closed by the 

 operculum. 



This species resembles T. (Arborella) dichotoma (Osburn, 1914: 

 202) from the West Indies, but has a much shorter ovicell and a broader 

 sinus. It is similar also to T. gryllus Canu and Bassler 1929:395 from 

 the Philippines, but the zooecia are only about half as long and the sinus 

 is much wider. 



