PEKNATTJLIDA OF THE MERGTJI ARCHIPELAGO. 283 



lodging the autozooids when retracted are black or dark brown. 

 Finally the stalk is shorter relatively to the rachis than in 

 Kolliker's specimen. 



The single specimen from Mergui is rather paler in colour 

 than the Andaman Islands examples, but agrees with these in 

 other respects. 



The axis in Lituaria (fig. 20) extends the whole length of the 

 colony. In the stalk it is slender, and ends below in a flexible 

 hooked extremity. Passing up into the rachis it gradually 

 increases in size, being thickest at its upper end. Along the 

 greater part of its length it is quadrilateral; wider from side to 

 side than dorso-ventrally, and grooved longitudinally on all four 

 faces. Its upper part presents laterally a number of cup-like 

 depressions, lodging the deeper parts of the polype-cavities. 

 These depressions, which increase in size and depth towards the 

 top of the axis, are separated from one another by thin sharp- 

 edged partitions, produced at places into prominent teeth (fig. 

 20), which during life come very close to the surface of the 

 rachis. 



In the young specimens (fig. 21), which vary in length from 

 13 to 19 millim., the fleshy ccenenchym of the rachis is very 

 scanty, and the polypes few in number. The axis is very well 

 developed, and its surface is deeply excavated to form cups for 

 the lodgment of the polypes, the partitions between the cups 

 coming quite to the surface, and forming a conspicuous mosaic 

 pattern. The top of the rachis and axis is pointed, and the 

 polypes are largest some little distance below it. In the 

 smallest specimen there are 10 well-developed polypes, but no 

 siphonozooids ; in the largest of the nine there are about 20 

 polypes and a few siphonozooids in addition. 



The principal dimensions of one of the adult specimens are 



as follows : — 



Length of colony 145 mm. 



Length of stalk ..... 62 



Length of rachis 83 



Diam. of top of rachis 5 



Diam. at junction of stalk and rachis ... 4 



Diam. of stalk 3*5 



Diam. of terminal vesicle 5 



LLNN. JOTTRN. — ZOOLOGY, VOL. XXI. 24 



