274 J- Playfair Mc Murrich, 



parieto-basilar miiscle. The longitiidiiial muscles are weak, tlieir 

 processes being* low and simple or but slig'htly branclied, and the 

 basilar muscles are hardly developed. The mesenteries of the first 

 and second cycles are sterile, while those of the third and fourth 

 are fertile. There seemed to be no outer stomata, although the 

 inner ones were quite distinct. 



There seems little reason for doubting that this form is identical 

 with the Actinia impatiens of Couthouy. In its external form, the 

 thickness and firmness of the column mesogloea and the occurrence 

 of tubercles, it sug-gests one of the PJwUiinae, but the complete ab- 

 sence of a cuticle and the fact that more than the primary cj^cle 

 of mesenteries are perfect excludes it from that sub-family. I cannot 

 State positively that cinclides are wanting. but a careful examination 

 failed to reveal tlieir presence and the thickness of the column wall 

 is against their occurrence as inconspicuous openings. 



17. Choriactis crassa n, sp. 



No. 627. \ Cabo Espiritu Santo ( 3 specimens. 



628. i East coast of Tierra del Fuego. l 2 specimens. 



All the individuals beloiiging to this species were strongly con- 

 tracted, having a dome-like form, with the disc and tentacles com- 

 pletely concealed (Fig. 62). The base is flat and of the adherent 

 type, and in some of the specimens lias fragments of hydroid stems 

 attached to it. The column walls are almost leathery in their con- 

 sistence and are quite smooth except at the summit where there 

 are from twenty to twenty-three radiatiiig ridges differing somewhat 

 in height, although no definite arrangement of the larger and smaller 

 ones could be made out. Ä slight circular fold separates the ridged 

 portion from the remainder of the column. No cinclides could be 

 discovered. 



On making a longitudinal section of the column it was evident 

 that a considerable portion of the distal part of the wall was 

 inverted (Fig. 63), forming a capitulum-like portion which was 

 distinctly ridged. The tentacles were rather numerous, moderate in 

 lieight and conical in form. Some were invaginated into themselves 

 and some projected down into the widely open stomatodaeum almost 

 to the base. 



The diameter of the base was about 1.4 cm, and the height of 

 the contracted column 0.5 cm. No trace of color persisted in any 



