THOMSON AND RUSSELL— AXIFEEA. 157 



The ccenenchyma forms a thin layer and is filled with rather stout warty spindles, which 

 liave a pebbly appearance. 



The verrucge are beehive-like, 2-2'5 mm. in basal diameter and l'5-2 mm. in height. 

 They are crowded on all sides of the stem and branches, being distant from one another 

 2-2'5 mm. The mouth of the verruca is frequently open, showing the undeidying 

 operculum. The spicules on the verruca wall are arranged longitudinally and overlap 

 one another like the slates on a roof. The mouth of the verruca is also surrounded by 

 an inconspicuous fringe formed by the projecting ends of the spicules. 



The polyps are completely retractile and possess a well-developed operculum, consisting 

 of eight " points," each composed of two pairs of convei'ging spicules, resting upon a 

 " crown," which consists of three rows of spicules. 



The spicules are white and are almost exclusively warty spindles, straight or slightly 

 bent. The warts are small, close-set, frequently truncated, and bear minute pointed 

 tubercles. The spindles seem to bo covered by fine longitudinal striations. A few of 

 the spindles approximate to the club type. The following measurements were taken of 

 length and breadth in millimetres: 0-44.X0-08, 0-84x0-16, l-04xO-23, l-62x0-28. 

 There are also some small slender curved spindles with scattered tubercles along one 

 side: O'SS X 0-035, 0-56 X 0-07. 



In a large dried specimen, 47 X 27 cm., the spicules were more irregular in form, and 

 more like those of typical species of Acis. Along with spindles there were clumsy Inroad 

 discs of irregular shape and others like rough pebbles. This is a good instance of the 

 way the spicules differ with the size and vigour of the colonies. 



Locality. Salomon, 60-120 fms. 



Key for the identification of the Species q/'Acis. 



1. Spicules squamous, or large fusiform spindles with fine warts ... 3. 



2. Spicules coarse warty spindles and clubs A. obscura. 



3. Colony branched 5. 



4. Colony unbranched A. solitaria. 



5. Colony erect 7. 



6. Colony depressed A. dejecta 



(spicules up to 4-5 X 2 5 X 1 mm.). 



7. Spicules witliout interlocking projections .9. 



8. Spicules with interlocking projections A. pustulata. 



9. Spicules small and oval A. alba. 



10. Spicules round and pebbly A. ceylonengis. 



11. Spicules with large tubercles A. orientalis. 



(Hickson's Acis sp. is near A. orientalis, but is yellow or red.) 



12. Spicules long (3 mm.) and fusiform, closely fitted A. alternam. 



13. Veirucse with projecting spines round the mouth 14, 15. 



14. Spines prominent A. spinosa. 



15. Spines irregular and not prominent A. indica. 



Note. — A. guadalvpensis, D. & M., is not included in the above Key, since we have not been 

 able to gather any details concerning it. 



21* 



