182 ACTINLK «H' A1J5ATKOS8 EXPLORATIONS M' MURRICH. 



(Icniis ADAMSIA Forlios, 



Sagartiii.T with adliovciit l»aso, the ectoderm of wliieh secretes a 

 iiu'inbrane; cohinin without warts or venucii-, but jirovided witli one (jf 

 two liorizoutal series of einelidal tubercles a short distance above the 

 linibiis; margin tentacuhite. 



26 Adamsia (?) involvens, «!•. nov. 



riiiti^ \X1\, ]'i,u.s. S'J niul S:{; I'hito \\\, I'i^. 85. 



No. TIG. Station, '21'X'>. L:it. 1 (>:>' N.: l(lll^^ SO- 15' \V. Di-ptli, 711 iathoin.s. 

 Twelve spe.ciuieiis. 

 Every specimen is liilly contracted and completely incloses a (ias- 

 teropod shell, being wrajtped around it in such a manner as to conform 

 itself more or less to the shape of -he shell ( IM. xxix, Figs. 82 and 83). On 

 this account it is diflicult to give any accurate measurement of the 

 height of the Actinian, hut this may be averaged for the coutracted 

 specimens at about 1.5 to 2'^'"-, and the diameter at from 1.25 to 1.5'"'. 

 The cohimu is of a pale flesh color, but becoming thinner toward the 

 limbus it has a darker shade, and is here longitudinally streaked with 

 whit<' lines, indicating the lines of insertion of the mesenteries on the 

 column wall. In litis Ihinner region, too, the internal organs shine 

 through. The tcnlaclcs :ire of a salmon color, this tint depending, to a 

 certain extent, and ]»robably entirely, on the bright leddish orange 

 pigment which occurs everywhere in the endoderm. The coloratiou 

 which these preserved- specimens present is entirely independent of any 

 colors which may have been ]>resent in the ectodt'rni, since this layer 

 has entirely disapi)earcd from tlie surface of the column. 



The base incloses the gastcropod shell, and, as it were, forms the 

 Oldening of the habitation <»f the mollusk. Its ectoderm secretes a 

 very well marked chilinous layer, not only over the regiou in contact 

 with the shell, bu( als()()Ver that which is free (Vom ii. 



The column wall is smooth through<»ut and has a i)arcliment-like con- 

 sistency, the mesoghea- being very fibrous in structure, though rather 

 thin. Xo einelidal tubercles could Ite ]»erceived. The sphincter muscle 

 (PI. XXX, I'^ig. 85) is well develoi>ed, though not very broad. Toward its 

 upp«'r nuirgiu the muscle cavities are in section more or less circular 

 in oulline and distinctly separated IVom one another, but lower down 

 they are more elongated and are separated by narrower partitions, cir- 

 cular scattered cavities lying upon the outer surface, it is separated 

 throughout from the endoderm by a thin layer of mesoghea. The circu- 

 lar nuiscles of the endoderm are only slightly developed, the cells being 

 aiianged in an almost smooth layer and not sup])orted on well-devel- 

 oi>ed processes of mesoghea. 



The margin is tentaculate, and the tentacles are ananged apparently 

 in three cycles, though their exact arrangement it is dithcult to ascer- 



