ACTINIANS OF GULF OF CALIFORNIA— CARLGREN 435 



As to the position of the cnidorages and acontia, there are no dis- 

 tinct differences because the acontia sometimes occur in other 

 places than at the end of the mesenteries. 



Family CERIANTHIDAE 



PACHYCERIANTHUS INSIGNIS, new species 



Marginal tentacles about 100. Directive labial tentacle (d) 

 present. Arrangement of labial tentacles 2(d) 413.4343. . . . About 

 8 mesenteries attached to the siphonoglyphs. Hyposulcus rather 

 well developed. Free part of the directives somewhat shorter than 

 the actinopharynx. Free part of the second protomesenteries ip2) 

 somewhat more than double as long as the free part of the direc- 

 tives. Third protomesenteries (p3) somewhat shorter than p2. 

 Several M and m metamesenteries reach down almost to the 

 proximal end of the body but diminish, as usual, in length toward 

 the multiplication chamber. B and 6-metamesenteries rather short. 

 Ciliated tract of the M and m-mesenteries distributed over almost 

 their whole length with craspedonemes, which in the upper and 

 lowest parts are more numerous than in the middle of the mesen- 

 teries. Craspedonemes of the ciliated tract on the B and &-meta- 

 mesenteries absent?; M and m-mesenteries fertile; the other mes- 

 enteries sterile. Nematocysts of the column partly 43.9-64.9 by 

 12.7-20.4 (22.6) /x, partly 42.3-49 by 7-10 fi (both atrichs), partly 

 48-56.4 by 11.3-14 /x (holotrichs, rare), partly (26.8) 31-43.7 by 

 5.6-7 fi (type a microbasic 5-mastigophors with a long thick shaft) , 

 partly 25.4-29.6 by 3.5-4.5 /a (type c microbasic &-mastigophors 

 with a short shaft) ; those of the marginal tentacles partly 24-35.2 

 by 5-5.6 fx (type a, very common), partly 19.7-24 by 3.5-4.2 /a 

 (both microbasic 6-mastigophors) ; those of the labial tentacles 

 partly 31-43.7 by 5-8.5 /., partly 22.6-28.2 by 3.4-4.2 ^ (both 

 microbasic 6-mastigophors), partly 29.6-35.2 by 5.6-7 fx. (atrichs, 

 rather common) ; those of the actinopharynx partly 29.6-41 by 

 5-7 fi (atrichs), partly 22.8-42.3 by 5.6-8.5 fi (type a, rather com- 

 mon), partly 26.8-36.7 by 3.5-4.2 /x (scarce), partly 15.5-19.7 by 

 3.5-4.2 [x (type c; all three microbasic 6-mastigophors) ; those of 

 the cnidoglandular tract of the filaments partly 26.8-35.2 by 5.5-7 ju, 

 (atrichs, rather common) , partly 22.6-32.4 by 6.3-8.5 fx (type a, 

 very common), partly 13.4-19.7 by 6.3-8.5 fx (scarce, both micro- 

 basic 6-mastigophors) ; those of the craspedonemes of the ciliated 

 tract 28.2-42.3 by 5-5.6 fx (microbasic 6-mastigophors, very 

 numerous) . 



Color in alcohol. — Column grayish red-brown, marginal tentacles 

 banded with stripes of red-brown, labial tentacles yellowish brown, 

 actinopharynx yellowish. 



