71 



ance of the specimen is due to the fact that the stalk is 

 completely covered by a milky white encrusting mass of the 

 compound Ascidian Leptoclinum speciosum (Herdman), 

 which so completely hides it that the Alcyonarian polyps 

 appear to spring from liat plate-like stolon encrusting a solid 

 white substance. An examination of sections of the colony 

 prove it to be a new species of the genus Heteroxenia Koll. 



The colony is 45 mm. high by 37 mm. in diameter at the 

 crown, cylindroidal in form, the stem covered with an 

 encrusting growth of the Tunicate Leptoclinum. The Auto- 

 zooids protrude about 6 mm. from the coenenchym, but are 

 in some cases retracted. The tentacles of the autozoids, 

 from 4-6 mm. in length, usually provided with one row of 

 8-10 pinnules on each side. The siphonozoids numerous and 

 not prominent. Spicules very scarce ; absent in the polyps ; 

 rarely more than 0.0 1 mm. in greatest diameter. The colour 

 in spirit is brown. 



Locality : False Bay, Cape of Good Hope. 20 fathoms 



Only one other species of this genus is known, namely, 

 Heteroxenia Elizabethae Koll, which occurs at Port Denison 

 (Kolliker) and Zanzibar (Bourne). Fortunately, in the 

 writings of Kolliker, Bourne, and Ashworth we have an 

 excellent description of the anatomy of this species. It 

 differs from our new species in the following characters : — 

 The exsert portions of the autozoids are much longer, 

 namely, 10-28 mm. in length, and their tentacles have three 

 rows of pinnules on each side. The siphonozoids protrude 

 about 2 mm. from the surface of the coenenchym, and are 

 provided with rudimentary tentacles. The spicules are 

 numerous in the autozooids. 



In some respects Heteroxenia capensis resembles H. rigida 

 May (11) from Mozambique, in which the polyps protrude 

 not more than 10 mm. from the coenenchym, and the ten- 

 tacles possess one row of pinnules on each side. The 

 specimen examined by May, however, was not very well 

 preserved, and no evidence of dimorphism was discovered. 



The number of rows of pinnules on the tentacles of the 

 polyps of the Xeniidae is the character which is undoubtedly 

 of some value in the determination of species but it presents 

 some difficulties. In some of the autozooids of Heteroxenia 

 capensis which were fully expanded there appeared to be 

 clearly one row of pinnules only on each side of the tentacles ; 

 but in others the pinnules were in two rows or irregularly 

 distributed on the margins. I am inclined to think that the 

 latter eflFect is partly if not wholly due to retraction. 



