512 REPORT ON THE XEXIIDAE COLLECTED BY DR WILLEY. 



in nearly the same proportion (9 — 12 in each row in Dr Willey's, 15 — 18 in Schenk's). 

 These differences are probably due to the fact that this specimen is a young colony 

 the polyps of which have not yet grown to their full size and the tentacles of which 

 have not yet acquired the full number of pinnules. (This is supported by the 

 condition of the genital products described above.) In spite of these differences the 

 characters of the colony, e.g. the shape and character of the stem, the form and 

 structure of the polj^s, the shape of the pinnules and the extraordinary abundance 

 of spicules, are in close agreement with the corresponding characters of Schenk's 

 species. 



This species has been previously recorded from Ternate (Moluccas). 



XENIA MEMBRANACEA. Schenk. 



This colony consists of two almost equal and parallel stems arising from a common 

 basal membrane which is attached to the two branches of a V-shaped, piece of dead 

 madrepore. The membrane which has spread out over the adjacent surface of the 

 madrepore is thickest around the bases of the stems, becoming gradually thinner towards 

 its free edge, where it is about a millimetre thick. The stems are 15 mm. long and 

 10 mm. in diameter, and 18 mm. long and 9 mm. in diameter respectively. The free 

 end of each stem is slightly convex and bears the polyps, which are numerous and 

 closely packed together, often being somewhat flattened by mutual pressure. 



The polyps are moderately long and have a slender appearance. The body of 

 each polyp is 5 mm. — 10 mm. in length (a very few reach 12 mm. in length) and 

 •8 mm. — 12 mm. in breadth. The tentacles are also long, slender and pointed, being 

 4"5 mm. — 7 mm. in length and about '4 mm. — "8 mm. broad. The inner face of each 

 tentacle bears rather long and thin pinnules, which are arranged, but not very clearly, 

 in six rows. The pinnules generally occupy the whole of the inner face of the 

 tentacle, but in a few polyps the middle line of the tentacle for a short distance 

 from the base is free from pinnules. There are, on an average, 16 to 18 pinnules 

 in each row, but in some of the longest tentacles there are 24 in each row. In 

 the middle of the tentacle, where they are largest, the pinnules are "5 mm. — 6 mm. 

 in length and about "1 mm. in breadth. 



In this specimen also buds are present but the}- are much fewer in number 

 than in the preceding colony (X. crassa). They are found only on the edge of the 

 polyp-bearing summit of each stem. The smallest is "4 mm. long and its tentacles 

 are but faintly indicated. In a, bud '6 mm. long the tentacles are finger-shaped lobes 

 •25 mm. long, while in a polyp 1 mm. long they have attained a length of So mm. 

 but none of them yet possess pinnules. A young polyp 1-4 mm. long has advanced 

 considerably, as its tentacles are '6 mm. long and show two or three pinnules on 

 each side of the middle line of the tentacle (seen from the outer aspect), while a 

 young pol\i3 25 mm. long bears tentacles 13 mm. in length, each of which shows on 

 its outer face 6 — 7 pinnules on each side of the middle line. 



The spicules are round or oval discs '012 mm. — -018 mm. in length and 01 mm. — 

 •012 mm. in breadth. They are either yellowish or slightly bluish-white by reflected 

 light and many of them show iridescent colours. By transmitted light the spicules 



