24 



VERPJLL ON THE POLYPS OF THE 



torn completely covered for acres with this species, from low-water mark to a depth of 

 two fathoms or more, and so thickly crowded on every exposed surface of rock that from a 

 stone no more than six inches in diameter I have taken upwards of sixty individuals of 

 various sizes. On the southern coast of Labrador we failed to detect this species during 

 numerous careful searches at low-water mark and while dredging in favorable situations. 

 It is not improbable, however, that it may yet be found there, as well as on the coast of 

 Newfoundland. This species, like M. dianthus, often separates from the border of its base 

 small fragments, which in a few days become perfect individuals. This is analogous to basal 

 budding, so often seen in other families of polyps. 



Genus Cereus Oken. 



Actinia {pars) Ellis and other early authors. Cereus Oken, Lehrb. der Nat. (1815, type 

 Actinia bellis Ellis and Sol.). Actinocerus Blainville, Diet. Sci. Nat. (1830) ; Man. d'Actinologie, 

 (1834). Cribrina [pars) Ehrenberg, Corall. roth. Meeres (1834). Sagartia (pars) Gosse, Trans. 

 Linn. Soc, xxi. p. 267 (1855). Cereus (pars) and Adamsia (pars) Milne-Edwards, Coralliaires 

 (1857). Sagartia (Scgphgia) Gosse, Actinologia Brit., p. 123 (1860). 



Column very contractile, pillar-like in expansion, capable of great elongation. Walls 

 extending to the margin, uninterrupted by a fold or thickening, pierced by numerous cin- 

 clidae, the upper part provided with numerous, well-developed suckers. Acontia emitted 

 freely. Tentacles very numerous, the inner ones somewhat scattered on the disk, the outer 

 crowded at the margin. Disk broad, scarcely frilled, though often undulate. 



In adopting the genus Cereus of Oken I find it necessary to change materially the limits 

 assigned to it by Milne-Edwards, and to take as the type of the group Actinia lellis Ellis and 

 Sol., which is the first species named by Oken, and the one which, more than any of the 

 others, possesses the characters mentioned by him, particularly the perforation of the walls. 

 This character does not appear to exist among those species included in section A of the 

 genus as defined by Milne-Edwards, which corresponds to Bunodes and Rhodactinia. The 

 group as here restricted embraces a part of the genus Sagartia of Gosse, but I am disposed 

 to consider those species of the latter genus claimed by him as most typical, worthy of 

 being separated generically under that name. The genus Cribrina of Ehrenberg appears to 

 be perfectly synonymous with Cereus as defined by Oken, although the first species named 

 under it has not the character of perforated walls assigned by him to the genus. 



Cereus sol Agassiz, MS. 



Actinia sol Agassiz, MS. 1849. 



The column is very changeable in form, in expansion often like a moderately elongated 

 pillar, enlarging both towards the base and summit. It is capable of contracting into a 

 globular form or into a low, flattened cone ; walls provided for a short distance below the 

 tentacles with well-marked suckers, towards the base nearly smooth. Acontia emitted to 

 the distance of two inches from scattered openings, apparently not very numerous. Base 

 adherent to shells, etc., somewhat expanded, circular, the tissue diaphanous, beautifully 

 marked by the internal radiating lamella?. Tentacles numerous, amounting to several hun- 

 dreds in large specimens, arranged in many indistinct circles ; inner ones largest, placed 

 about midway between the mouth and the border of the disk, about one-half an inch in 



