440 PROCEEDINGS OF THE NATIONAL MUSEUM vol. loi 



Color. — Yellowish gray. 



Measurements. — Length 12.5 and 10 cm., respectively; breadth 

 in their uppermost part 1.2 and 0.8 cm., respectively. 



Cotypes. — Two specimens, U.S.N.M. No. 49445, Gabriel Bay, 

 Espiritu Santo Island, April 12, 1940. 



PALYTHOA RICKETTSI, new species 



Figure 83, a, h; Plate 14, Figure 11 



Coenenchyme thin. Polyps robust, elongate, closely set (pi. 14, 

 fig. 11) incrusted with grains of sand occupying the continuous 

 ectoderm and the outermost part of the mesogloea only. Mesogloea 

 of the column with cells and very numerous cell-islets often show- 

 ing tendency to be arranged in an annulus toward the endoderm. 

 (Figure 83, a, shows a transverse section of a part of the column) . 

 Ridges of the scapulus about 30-32 in larger specimens. Sphincter 

 forming a row of rather broad meshes transversely set. Ectoderm 

 of the column, tentacles, oral disc, and cell-islets provided with zoo- 

 xanthellae. Tentacles seemingly without spirocysts. Siphonoglyph 

 strong. Mesenteries in large specimens about 66. No holotrichs 

 and no pigmented cells in the lower part of the mesenterial canals, 

 but holotrichs are present although very rare in the upper part. 

 Nematocysts of the tentacles partly 41-48 by 19.5-21 (24) ix. (holo- 

 trichs, few), partly about 28 by 2.8 (x (microbasic &-mastigophors, 

 very rare) ; those of the actinopharynx 30-39.5 by 4.2-5 ix (micro- 

 basic 5-mastigophors) ; those of the filaments partly 49.3-56 by 

 22-25.4 iJi (holotrichs, few), partly 29.6-40 by 4.2-7 yn (micro- 

 basic 2?-mastigophors), partly 42.3-56.4(60.5) and 3-3.5 /x (micro- 

 basic 6-mastigophors) . 



Color in alcohol. — Gray with scattered black and yellowish 

 grains of sand. 



Measurements. — The largest polyp, contracted, is 2 cm. in 

 length, 0.9 cm. in breadth at uppermost part. 



Types. — Holotype, a small colony, U.S.N.M. No. 49440, south 

 of Tiburon Island, April 3, 1940. Paratype, a small colony, 

 U.S.N.M. No. 49441, same data. 



PALYTHOA IGNOTA, new species 



Figure 83, c, d; Plate 14, Figure 12 



Coenenchyme rather thin. Polyps more or less closely set (pi. 14, 

 fig. 12) in contraction, somewhat longer than broad, robust, 

 strongly incrusted with grains of sand penetrating almost the 

 whole mesogloea of the column (fig. 83, c) . Ectoderm of the 

 column rather thin, mesogloea with cells but with few cell-islets. 

 Ridges of the scapulus incrusted. Sphincter very elongate, of about 

 same appearance as that of P. ignota. Cell-islets, ectoderm and 



