ACTINIANS OF GULF OF CALIFORNIA— CARLGREN 



441 



endoderm of the column, ectoderm of the tentacles with that of 

 the actinopharynx without zooxanthellae. Tentacles with spiro- 

 cysts. Siphonoglyph and hyposulcus strong. Mesenteries in large 

 specimens about 50-58 (51 in a sectioned specimen; in the largest 

 specimen there are 58 tentacles and therefore the same number of 

 mesenteries). Micromesenteries well developed. No pigmented 

 cells but numerous holotrichs in the mesenterial canals. Figure 

 83, d, shows a macromesentery seen from the side (inner side 

 on the left) . Nematocysts of the tentacles 21-31 by 3.5-4 fi (micro- 

 basic fe-mastigophors) ; those of the filaments partly 51-62 by 

 19.7-21 /x, partly 15.5-17.6 by 3.5-4 ^ (both holotrichs), partly 

 18.3-21.8 by 4.2-5.6 /a (microbasic j^-mastigophors) , partly 49.3-65 

 by about 4 /x (microbasic 6-mastigophors). 





Figure 83. — a, h, Palythoa rickcttsi, new species: a, Transverse section of column; b, 

 macromesenterj' seen from the side, c, d, Palythoa ignota, new species: c. Section of 

 column; d, macromesentery seen from the side (inner side to left). 



Color in alcohol. — Grayish. 



Measurements. — Larger polyps, contracted, 1.2 cm. in length, 

 0.7-0.9 cm. in breadth. 



Holotypc. — One colony, U.S.N.M. No. 49541, Angeles Bay, April 

 1, 1940, on rocks. 



PALYTHOA INSIGNIS, new species 



Figure 84, a-c; Plate 14, Figure 13 



Polyps somewhat elongate, of different size, connected with a 

 rather thin coenenchyme (pi. 14, fig. 13). Ridges of the scapulus 

 24-32, incrusted. The ectoderm and the outer part of the meso- 

 gloea of the column incrusted with grains of sand. Mesogloea of 



