THE ACTINIANS OF PORTO RICO. 
343 
Genus ASTERACTIS Verrill. 
Asteractis, Verrill, 1869, p. 464; 1899, p. 45; Andres, 1883, p. 506; Haddon, 1898, p. 439. 
Phyllactidse in which the column is provided in its upper part with vertical rows of adhesive 
verruca;; outside the tentacles the acrorhagi are enormously developed, appearing as a flat, lidded 
collar, and each bears numerous small hollow papillre or finger-like simple or complex outgrowths. 
Sphincter muscle circumscribed. Twelve or more pairs of perfect mesenteries. 
Asteractis expansa Duerden. Pis. II, VIII, IX, Figs. 8, 29-33. 
Asteractis, n. sp., Duerden, 1898 a, p. 455. 
Asteractis expansa, McMurrich, 1898, p. 232. 
This species is one of the most plentiful in the collections from Porto Rico, but all the specimens 
received are strongly retracted and infolded. It is undoubtedly the form which is to be obtained in 
such abundance all around the Jamaica coasts, and which has been discussed and partly described by 
McMurrich (1898, p. 232) from twenty-six specimens obtained by him from Cuba. On account of 
the uncertainty involved in its identification with others already described it is desirable that a full 
account of its characters should be given. I have therefore supplemented the study on the Porto 
Rican examples with other details obtainable from living Jamaica specimens. A discussion of its 
relationship with other species is given at the end of the description. 
The usual living condition of the polyps is that of an exposed circular disk at the level of the 
sea-floor in very shallow water, the remainder of the animal being completely buried. The base may 
be fixed to rocks or stones, or merely adherent to loose fragments. When the polyp is only embedded 
in gravel and sand it can readily be secured by passing the fingers downward and around it and then 
lifting up the entire mass. When thus collected the whole of the upper part of the column is thickly 
coated with sand, fragments of shells, and small pebbles, held there by means of verruca;. The 
foreign matter is slowly dropped if the column remains exposed in the laboratory for some time. 
Placed in a tumbler or vessel, the upper part of the column, along with the acrorhagi, overhangs 
gracefully, its form and the delicacy of the colors rendering the polyp a very attractive object. It was 
from such a specimen that fig. 8, pi. ii, was taken. 
In the laboratory the polyps exercise some selection in their food, anything objectionable being 
dropped over the edge as a result of the contractions of the latter. Should the water become stale 
the stomodaeum is everted, and if no change is made in its surroundings the eversion of the polyp may 
become complete, enabling all the internal organs to be observed. The exposed colors vary with the 
nature of the sea-floor, the general impression being dark olive on a black muddy floor, and gray in 
coral mud or sandy surroundings. 
External characters . — When the polyps are expanded in the laboratory, free from foreign material, 
the base is larger in diameter than the column and pellucid, the mesenterial lines showing through. 
The margin is crenate. 
The column is erect and cylindrical, narrow in the middle, and broad below and above. It 
is thin-walled and divided by the mesenterial lines into well-marked rounded ridges and furrows, 
especially toward each extremity. Distally the column is caliciform and considerably overhangs the 
lower part. The verrucre are circular and extend in longitudinal rows down the intermasenterial 
ridges for about one-third of the length of the column, each ridge possessing about a dozen. The 
members of any row are usually irregularly arranged with reference to the contiguous rows, butsome- 
times they are disposed in transverse cycles. The middle of the verruca is usually depressed, giving a 
sucker-like character to the whole organ. 
The oral disk, regarding as such all the flat exposed part of the polyp, consists of three areas: 
(«) A peripheral zone, constituted of radiating, frondose bodies — the acrorhagi, in diameter occupying 
from one-half to two-thirds of the whole disk, and corresponding in number with the tentacles. 
( h ) The tentaculate zone, containing four cycles of subulate tentacles, (c) The usual smooth naked 
area of the disk or peristome, with the mouth in the center. 
The frondose areas are broad radiating bands, closely arranged, but sharply separated from one 
another by deep, naked grooves, mesenterial in position, and only seen on actually separating the 
ridges. They are raised a little above the general level of the disk, and are partly distinct from one 
