X, D, 1 Light: Philippine Alcyonaria, III 7 



0.02 to 0.04 millimeter in diameter in the cortex of the midstem 

 and average about 0.3 millimeter in length. They have a dis- 

 tinct central axis which extends into the projections. The pro- 

 jections, which are bluntly conical or flattened in the line of the 

 short axis of the spicule, reach a length at the center of the 

 spicule of 0.025 millimeter and are usually flattened or divided 

 in that region. The ends of these spicules are irregular and us- 

 ually flattened and divided. Scattered among these larger spic- 

 ules are a few small rod-shaped spicules bearing a few broadly 

 cone-shaped projections near each end. These spicules average 

 0.07 millimeter in length and 0.01 millimeter in diameter. 



The canals of the stem radiate from the center, where there 

 is a small central cavity between their converging walls. The 

 larger canals are usually found near the center, and the peri- 

 pheral canals are usually small. Those portions of the walls of 

 the inner canals which lie near the center of the stem contain 

 a few large slightly curved spindles and an occasional triradiate 

 form covered with small closely crowded projections. The 

 spindles reach a length of 0.8 millimeter and a diameter of 

 0.1 millimeter. 



In life the entire colony is green shading into light yellow 

 on the stem and base. In formalin the green fades, leaving the 

 polyp-bearing portion light yellow and the stems white. 



Locality. — Collected by Light from the shallow reefs in Taytay 

 Bay, Palawan. 



Type. — No. C. 2097 in the zoological collection of the Univer- 

 sity of the Philippines. 



This species agrees very closely with L. philippinensis in the 

 size and shape of the spicules and in their distribution. The 

 spicules are much more numerous in L. rigidum, however, than 

 in L. philippinensis. Lithophytum rigidum differs from L. phil- 

 ippinensis, also, in that its polyps are consistently smaller and 

 in the form and consistency of the colony. This is not a dif- 

 ference due to contraction as might be supposed, for I have had 

 the opportunity of observing and collecting the living colonies 

 of the two species and the difference is even more striking there 

 than in the preserved material. The much longer and very 

 flexible colonies of L. philippinensis are treelike with long slender 

 branches and twigs, the whole colony waving with every current 

 of water, while the colony of L. rigidum is short, bushy, and 

 stiff, maintaining a fixed position; its stem and branches are 

 short, thick, and plumply rounded and the polyp-bearing portion 

 is mainly confined to the distal region of the colony. 



