514 REPORT ON THE XENIIDAE COLLECTED BY DR WILLEY. 



at the base. The stem widens as it ascends and its breadth at the summit is 

 33 mm. x 16 mm. The pol3rp-bearing area is slightly convex. The base of the colony 

 is prolonged downwards at the edges, forming an almost hemispherical cap which is 

 closely applied to the rock on which the colony is fixed. 



HI. The smallest colony consists of a single stem about 15 mm. long and about 

 12 mm. X 10 mm. at the base. 



The polyps arise moderately close together on the end of each stem. The bodies 

 of the fully developed ones are 5 mm. — 10 mm. long (a few reach 13 mm.) and 

 1"2 mm. — 1-8 mm. wide. The tentacles are long, being 5 mm. — 8 mm. in length and 

 1"3 mm. — 16 mm. broad, and bear on each side of the middle line three rows of 

 pinnules of about 2"2 — 29 in each row. The pinnules are long and slender, ".5 mm. — 

 "8 mm. in length and 1 mm. — '12 mm. in width. The inner face of each tentacle 

 presents an area free from pinnules. This area is about "4 mm. wide at the base of 

 the tentacle, gradually narrows towards its tip, and is no longer recognisable in 

 the distal fourth of the tentacle ; in this region the pinnules of the two sides are in 

 contact at their bases. 



Buds are found not only round the edge of the summit of the stem but also 

 scattered over the whole of the summit between the bases of the older polyps. 

 Those round the edge of the summit are similar to the buds found in other species 

 of Xenia (PI. LIII. Fig. 10), except that the young polyp is l^B mm. — l^S mm. long and 

 its tentacles have reached a length of nearly 1 mm. before the first pinnules appear 

 upon them. In the other species of Xenia the pinnules appear when the polyp is 

 much smaller and its tentacles are only "4 mm. — '6 mm. long. There are on the ends 

 of two of the large stems three small areas in each of which four or five buds are 

 found. Several of these buds differ from the normal buds present round the edge 

 of the summit of the stem, the body of the former being much larger in jH-opor- 

 tion to the tentacles than is usual. One of these buds is represented in Fig. 12. 

 Its total length is 5 mm., its stout finger-shaped, rather unequal tentacles are only 

 1"0 mm. to 1'3 mm. long. Three of them are trilobed at their tips, i.e. there is an 

 indication of the formation of the first two pinnules, one on each side of the axis 

 of the tentacle. Another similar bud G nun. long has slender digitiform tentacles 

 17 mm. long, each of which bears one or two pinnules on each side of the middle 

 line (see Fig. 11). In these and other similar buds from the three areas mentioned 

 above, the tentacles are onh- about one-fourth of the total length of the polyp and 

 bear few pinnules, whereas in - buds of similar size present round the edge of the 

 summit of the stem the tentacles are about one-half the total length of the polyp and 

 bear a larger number of pinnules. (See Figs. 10 and 11 ; the tentacles of the two young 

 polyps rejjresented are equal in length.) 



Few spicules are present in the stem except at the base, where they are numerous 

 and stand almost in contact with each other. The ■pre.sence of many spicules in this 

 region gives additional strength and rigidity to the basal portion by which the colon}' is 

 attached to the rock. Spicules are moderately numerous in the body of the polyp, 

 becoming more numerous towards its distal end. They are abundant on the outer 

 faces of the tentacles and pinnules, being close together in the latter. The\' are less 



