442 PROCEEDINGS OF THE NATIONAL MUSEUM vol. loi 



the column with cells and extraordinarily numerous cell islets (fig. 

 84, a). Sphincter strong, forming a single row of meshes (fig. 84, 

 b). Tentacles with numerous spirocysts. Siphonoglyph well de- 

 veloped, hyposulcus strong. Mesenteries some up to more than 60. 

 A sectioned specimen has 62 (32 + 30) mesenteries, another about 

 60. Numerous pigmented cells and holotrichs in the mesenterial 

 canals. Figure 84, c, shows a macromesentery in its lower part 

 (inner side to the right, the pigmented cells are not figured). 

 Ectoderm of the column, tentacles, and oral disc with zooxanthellae. 

 Nematocysts of the column 45-57.8 by 22.6-28.2 fx (holotrichs) ; 

 those of the tentacles partly 18.3-24 by 3-4.2 /x (microbasic b- 

 mastigophors), partly 46.5 by 21 /x (holotrichs, very rare) ; those 

 of the actinopharynx 25.4-39.5 by 3.5-4.2 fi (microbasic &-masti- 

 gophors) ; those of the filaments partly 24-29.6 by 4.2-5.6 (micro- 

 basic 25-niastigophors, common), partly 39.5-52.2 by about 4.2 ix 

 (microbasic 6-mastigophors), partly 48-53.6 by 19.7-21 fx (holo- 

 trichs, very rare) ; those of the mesenterial canals 50-52.2 by 19.7- 

 22.6 fx (holotrichs, numerous). 



Measurements. — The larger polyps are 1.5 and 1.3 cm., respect- 

 ively, in length, and 0.7 and 0.8 cm., respectively in breadth. 



Cotypes. — Two colonies, U.S.N.M. No. 49540, Coronado Island, 

 March 27, 1940. 



PALYTHOA PAZI. new species 



Figure 84, d; Plate 14, Figure 14 



Polyps connected with a rather thin coenenchyme (fig. 84, d) , 

 incrusted with grains of sand occupying almost the whole meso- 

 gloea of the column. Mesogloea with rather numerous cells and 

 cell-islets. Ridges of the scapulus distinct in the larger polyps 

 and about 27-30 in number. Ectoderm of the column, tentacles, 

 and oral disc with zooxanthellae. Tentacles with numerous spiro- 

 cysts. Siphonoglyph strong. Mesenteries in large specimens up to 

 about 60. Mesenterial canals with holotrichs and pigmented cells. 

 In figure 84, d, the lower part of a macromesentery is reproduced, 

 the pigmented cells are not figured (inner side on the left) . Nema- 

 tocysts of the actinopharynx 24-33.8 fx (microbasic 5-mastigo- 

 phors) ; those of the filaments partly 28.3-31 by 4.5-6.3 /x (micro- 

 basic ??-mastigophors), partly 35.2-50.8 by 4.5-5 [x (microbasic 

 ?)-mastigophors), partly 45-50.8 by 21-24 fx (holotrichs, very 

 rare) ; those of the mesenterial canals 49.3-55 by 19.7-22.5 fx 

 (holotrichs). 



Measureme7its. — Largest polyp, 1 cm. in length, 0.7 cm. in 

 breadth; another polyp is 1.1 cm. in length, 0.6 cm. in breadth. 



Holotype. — One colony, U.S.N.M. No. 49444, La Paz, on cal- 

 careous rocks, March 14, 1940. 



