REPORT ON THE ACTINIARIA. 15 



Hoi'mathia delicatula* sp. n. (PI. II. figs. 1, 3, IV. fig. 9). 



More than IGO tentacles; parietal spherules tentacle-like, one of the latter to 

 about every four tentacles. 



Habitat. — (?) (Inscription on the label completely soaked awa}'.) Two specimen.s. 



Dimensions. — Diameter of the nearly spherical body, 2'5-3'0 cm. 



Gosse has conferred the name of IlonnatUia margaritlue on an Actinian brought 

 up by the line of a deep-sea fishing-boat. Having obtained but one specimen, and that 

 not till some time after death, he could give but an incomplete description ; the most 

 important point of which is that on the delicate body-wall, at some distance from its upper 

 edge, are placed prominences resembling marginal spherules, the number of which is 

 about ten, and is essentially less than that of the tentacles. In his monograph treating 

 of the Actiniae, Angelo Andres has included the animal among the doubtful genera, as 

 being of uncertain systematic position. It was therefore very agreeable to me to find 

 in the Challenger material two Actiniae obviously belonging to the genus Hoiraathia, 

 by the study of which I am enabled both to justify the creation of a new genus, and 

 also to define accurately its systematic position. 



Both specimens were so strongly contracted as to resemble an apple in shape. 

 The upper part of the body-wall, the pedal disc and the mouth being entirely drawn 

 in, and the latter covered over, one saw at first only the lower part of the body-wall, 

 the smooth surface of which was so little characteristic that I came near to ranking the 

 animal among the undeterminable forms. Only after dividing a specimen longitudinally 

 did the circlet of parietal spherules come into view, their position Ijcing characteristic 

 of the genus Hormathia. 



The pedal disc is strongly constricted and pleated by the violent contraction. 

 The body- wall is exceptionally delicate, so that the septa are plainly vi-sible through it, 

 and is quite smooth. By a circular fold, which recalls to mind the boundary between 

 body-wall and oral disc, and marks the limit of retraction in a withdrawn specimen, is 

 bounded a separate invaginable region of the body- wall ; close up to this fold, and on 

 the side nearest to the oral disc, is placed a circlet of 42 knobs, which are hollow and 

 beset with nematocysts, and which tlierefore recoil the structure of the marginal vesicles 

 or "bourses marginales" (PI. IV. fig. 9). They are of difl'erent sizes, the largest 

 generally longer than the marginal spherules ; and are curved in a digitate manner at 

 the end, so as to present some resemblance to tentacles. The number of tentacles and 

 mesenteries being about 160, the parietal spherules, as I term these structures, are not 

 placed, like the marginal spherules, one on each inter- and intra-mesenterial chamber ; 

 but there is one spherule to about every four chambers, with one of wliidi it is 

 always in communication, leaving the remaining two or three free. 



The marked retractibility of the animal is effected by a sphincter muscle in a 

 definite region of the body-wall, which, commencing at some little distance from the 



