Actiniae. 295 



tentacles, the character of the sphincter muscle in both species is 

 more in accordance with that of Urticina crassicornis, the paradigm ^ 

 of the genus Urticina, than with that of B%inodactis verrucosa, the 

 paradigm of the genus Bunodactis. I consider the character of the 

 sphincter of more importance than the pentamerous or decamerous '^ 

 arrangement of the tentacles and mesenteries, and am of opinion 

 that this latter character should not be retained as diagnostic of the 

 genus Urticina, as suggested by Mr. Haddon (3 p. 445), and I have 

 therefore placed the two new Antarctic species under the genus 

 Urticina, 



Family BUNODACTIDJE. 



Urticina svilcata. 



External characters. — The specimens are all greatly contracted, 

 and in most cases the oral disc and tentacles are entirely hidden. 

 The colour of the preserved specimens is a dirty brown with a 

 distinctly green cast. There is no record on the collectors' labels as 

 to colour of this species when living. The column is soft to the 

 touch and is covered with verrucse, which in the contracted state of 

 the specimens are closely packed together. They are largest in the 

 equatorial zone and slightly diminish in size above and below. 

 There are forty-eight vertical rows, corresponding in position with the 

 inter- and intra-mesenteric spaces. 



In female specimens a distinct modification of the upper portion 

 of the column is noticeable. The body-wall in its upper third is less 

 firm to the touch, thinner, and the verrucfe are almost obliterated by 

 longitudinal furrows which run from a well-marked constriction ^ 

 (fig. 1) to the parapet, where they are deepened and intensified in 

 the more contracted specimens. Male specimens also show this 

 modification of the body- wall, but in a much less marked degree. 



On some of the specimens gravel and sand particles are still 

 adherent to the verrucse. In the healthy living condition, doubtless, 

 a continuous layer of foreign particles is formed around the column. 



The foot disc is distinct and muscular. 



The largest specimens measure 5 cm. in height, 5 cm. in diameter 

 at widest part, and 3 cm. diameter of foot disc. 



^ [The aui lior prefers this word to the more generally useil " type." — F. J. B.] 

 2 Prof. Verrill states (7, IV., p. 216) tliat he has found many si)ecimens of 

 Urticina crassicornis hexamerous, both as to tentacles and mesenteries, and other 

 workers have shown that whenever it was possible to examine a large nmiibei' of 

 specimens of the same species a great amount of variation existed in this respect. 



' This constriction marks the zone of invagination of the body-wall to form the 

 " brood chambers " (see p. 301). 



