232 



(4) Irregular crosses, 01 x 0'075 ; 0"175 x 0"1. 



(5) Slightly spiny spindles of authocodice, 0'25 x 0"025 ; 0-22 x 0'02. 



The number of epizoic animals is remarkable ; acorn shells are very 

 abundant, barnacles, crinoids and worm-tubes are not infrequent, while here and 

 there incrustations of Polyzoa are to be seen ; one young jjearl oyster is also 

 attached. 



Locality : Andamans. 



GENUS ACIS, Duch. an.l Mich. 

 Acis ceylonensis, Thomson and Henderson. 



In the collection there are a number of specimens which, though they show 

 the most diverse modes of branching, must nevertheless be grouped together 

 under this species. All are attached to small loose pebbles, except one which 

 has its disc of attachment on a piece of coral. The following are short descrip- 

 tions of a few types of colony : (1) Simple, lo cm. long with a basal diameter of 

 1-25 mm. (2) Simple, 2'5 cm. long and 2-25 mm. in diameter at the base. (3) 

 Complete branched colony, 9 cm. long and 2 cm. broad. The lower 4 cm. are bare, 

 but beyond this branches are given off subalternately in one plane. These arise 

 nearly at right angles, but bend upwards and continue sub-parallel to the main 

 stem. (3c/) Two other more delicate colonies have this type of branching, but in 

 neither is there such a long space devoid of branches. They measure 5"5 cm. in 

 height and 25 cm. in breadth, and 3 '5 cm. high by 1-5 cm. broad. (4) Complete 

 colony 3'5 cm. in height. The main stem is 11 cm. in length where it bifurcates, 

 one of the arms again giving origin to a small twig in the same plane. (5) Several 

 colonies branched in one plane somewhat like (4), liut there are frequent bifurca- 

 tions, the smaller twigs, however, coming off irregularly. (6) A number of the 

 colonies are branched in all directions, the l)ranches sinuous and crossing but 

 not fusing. It is interesting to note that specimens (1), (2) and (3) arise together 

 from a single spreading base. 



In spite of this diversity in branching there is no difference in polyps, 

 spiculation, etc. The diameter of the branches hardly varies throughout their 

 entire length except that the tips are club-shaped. 



The cojnenchyma is thick and has a rough arenaceous appearance. It is 

 composed of large thick warty spicules which overlap in all directions, the 

 largest measuring about 0-6 mm. by 0-3 mm. In some places they form an 

 almost uniform layer and present a tesselated structure. 



The polyps occur over the whole surface of the stem and branches at 

 intervals of about 2 mm. They measure 1 mm. in height and TS mm. in 

 diameter at the base. When expanded the verructe are cylindrical, but when 

 closed are dome-like. The spicules are arranged longitudinally and in some 



