REPORT ON THE ACTINIARIA. 15 



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



More than 160 tentacles ; parietal spherules tentacle-like, one of the latter to 

 about every four tentacles. 



Habitat. — (?) (Inscription on the label completely soaked away). Two specimens. 



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



Gosse has conferred the name of Hormathia margarithm 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 descrijation ; 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 tliat 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 Actinise obviously belonging to the genus Hormathia, 

 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 moutli being entirely drawn 

 in, and the latter covered over, one saw at first only the lower part of the I)ody-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 longitudinal!}' 

 did the circlet of parietal spherules come into view, their position being cliaracteristic 

 of the genus Hormathia. 



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

 The body-wall is exceptionally delicate, so that the septa are plainly visible 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 body-wall and oral disc, and marks the limit of retraction in a withdrawn specimen, is 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 bod\--wall ; dose up to this fold, niid (Hi 

 the side nearest to the uvi\\ di.^r. is pl.-iced a link't of 42 knoks, which arc hullnw imd 

 beset with nematocysts, and which tiierefore recall the structure of tiie marginal vesicles 

 or "bourses marginales" (PI. IV. fig. 9). They are of diflcrent sizes, the large.'it 

 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 al)uut IGO, the parietal spherules, as I tei-m these structures, are not 

 placed, like the uhirgiual s^jherules, one on each inter- iind intra-mesenteri.il chamber; 

 but there is one spherule to about every four chambers, with one of wliieh 1 1 is 

 always in communication, leavino; the remaining two or three free. 



'J'lie marked retractibility of the animal is efi'ectcd by a sphincter muscle in a 

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



