PE^ATULIDA OF TIIE MEEGT7I AECHIPELAGO. 



273 



are directed across the ventral surface, and they may overlap 

 (fig. 8). In the mature leaves the rays are well developed, from 

 16 to 22 in number, and project as very obvious spines. The 

 autozooids are arranged in 3 or 4 rows along the margins of both 

 surfaces of the leaf, and the mouths of the cells are pigmented. 

 There is a well-developed marginal zooid plate present in all 

 cases, usually markedly dentate along its distal margin, and con- 

 sisting of small, usually colourless siphonozooids. Larger sipho- 

 nozooids, usually pigmented, are irregularly distributed over the 

 basal portion of the zooid plate, and also over the upper surface 

 of the leaf ; a well-marked ventral zooid stripe is present at the 

 base of each leaf (fig. 8). The dorsal zooid stripe of the rachis 

 is short, does not extend below the 3rd or 4th 'pair of leaves, 

 and consists of 2 or 3 rows of siphonozooids. 



Our specimens fall into two well-marked groups, which we 

 propose to describe as varieties. 



Pt. chi^e^se, var. a. (Plate XXII. figs. 7-9.) 

 Of this form there are nine specimens, all from the Andaman 

 Islands. 



The general ground-colour is brownish yellow; the stalk is 

 mottled with purplish spots ; the leaves are yellow, with the 

 polype-mouths and the larger siphonozooids purple. This general 

 yellow colour dotted with purple spots is very characteristic of 

 all ten specimens. 



The feather is oviform to triangular in outline, and widest close 

 to its lower end. The rachis is wide, especially near its lower 

 end ; the stalk is shorter than the rachis, and thick. The lower- 

 most leaves are markedly spatulate, and those of the two sides may 

 overlap one another on the ventral surface of the rachis (fig. 8). 



The mature leaves (fig. 9) are of moderate thickness, and are fan- 

 shaped, the ventral border being nearly straight and the tip very 

 slightly hooked. The rays are 16 to 22 in number ; they are 

 not very conspicuous on the under surface of the leaf, but project 

 beyond its edge as stout marginal spines arranged somewhat 

 irregularly, and obviously consisting of bundles of smaller 

 spicules. 



The zooid plate (fig. 9) is large ; it extends along two thirds of 

 the length of the ventral border of the leaf, and is continued 

 along the rays so as to present a strongly toothed margin. The 

 ventral zooid stripe is well developed, and present in all the 



