520 EDITH M. PRATT. 



correlated with the reduced size of the tentacles and the absence of ventral and lateral 

 mesenterial filaments. 



8. Sclerophytum capitale sp. nov. (PI. XXVIII. fig. 8, PI. XXIX. figs. 15—17). 



Two specimens were obtained fi-om the reef at Hulule, Male Atoll, from shallow water. 

 One specimen is complete (fig. 8), the other has a portion of the stalk and capitulum 

 missing. The complete specimen is attached basally to a fragment of hard coral. 



The colony is fairly large, broad and laterally compressed, with a beautifully lobed 

 convex capitulum. The lobes are numerous, many of them are laterally compressed ; some 

 are branched. The colony is 65 mm. high, and 70 x 35 mm. broad. The stalk is irregular 

 in outline at the base, but the sides are rounded unbroken, and granular to the touch. 

 The height of the stalk is 27 mm. and the breadth is 43 x 29 mm. The colour of both 

 specimens in spirit is yellowish-grey. 



Spicules. Clubs and slender spindles are crowded near the surface as in other species 

 of Sclerophytum. Most of the clubs have small knotted heads (fig. 15) and are about '18 mm. 

 in length. A few clubs occur, which are bi- or tri-ramous; they are slightly longer and 

 more slender than those of Sc. densum. The tuberculate spicules (fig. 16) are smaller and 

 less numerous than in many species of the genus. In the capitulum they are 1 — 2'5 mm. 

 in length, but they are a little larger in the stalk, where some of them attain a length 

 of 3 mm. These spicules vary considerably in shape as well as size (fig. 16); regularly and 

 irregularly curved spindles are numerous. Crescentic, Y and K-shaped spicules also occur, 

 as well as a few spicules irregularly forked at both ends. 



The autozooids are larger in this than in many species (Table I. p. 531), an ex- 

 panded zooid measuring about 1 mm. across the crown. They are very regularly distributed 

 over the surface of the capitulum, but they are slightly more numerous on the tips of the 

 lobes, where growth is apparently most vigorous. In vertical sections they appear to be 

 very long and slender, broadest at the surface and tapering gradually posteriorly. 



The tentacles are apparently longer than in any species except Sc. palmatum, when fully 

 expanded measuring about "45 mm. in length by '2 mm. in breadth. They are broadest at 

 the tip and are not bluntly conical in the preserved condition as in other species. The 

 tentacles like those of Sc. palmatum are interesting because they have a double row of 

 pinnules down each side (fig. 17 tent.), in this respect approaching the genus Xenia. 



The stomodaeum is long and convoluted, and the mesenteries are all well-marked. All 

 have mesenterial filaments. The dorsal ones are similar to those of other species. The 

 ventral and lateral mesenterial filaments are short but are clearly marked. A partially 

 digested mass of food material containing a few zoochlorellae in the process of disintegration 

 was observed in the coelenteric cavity of one of the autozooids. 



Siphonozooids are present in this species (figs. 17 and 19, si.), but they are rudimentary. 

 They are, however, larger in this than in any other species of the genus which I have 

 examined. Many of them have an extremely small stomodaeum, which in sections is seen 

 to open to the exterior. They terminate posteriorly in the transverse vessels of the superficial 

 canal system. Zoochlorellae occur in the endoderm and the superficial canal system, but 

 they are not numerous in the coelentera nor in the lumen of the canals. 



