4' 



Spicules. These are all warty spindles, many of which are curved. Some of the spindles 

 in the ccenenchyma of the branches are the largest of any in the genus, attaining a length of 

 4 mui. They are all heavy, closely tuberculated and opaque. Those in the outer layer of the 

 coenenchyma are longitudinally disposed and close set, leaving little vacant space between them. 

 Their edges, however, are not closely fitted as in some species of Acis. 



Color. The colony is light brown, silvered by the spicules. Axis dark brown, spicules 

 colorless. 



Acis Duchassaing et Michelotti. (Modified). 



Acis Duchassaing et Michelotti. Mémoire sur les coralliaires des Antilies, 1860, p. 19. 



Acis Ridley. Annals and Magazine of Natural History, Series V, Vol. 10, 1882, p. 126. 



Acis Kölliker. Icones Histologicae, Part. II, 1865, p. 136. 



Acis Wright and Studer. Challenger Reports, the Alcyonaria, 1889, p. 111. 



Acis Thomson and Henderson. Ceylon Pearl Oyster Reports, Alcyonaria, p. 299. 



The original definition for this genus is as follows : — 



"Ce genre, que nous croyons nouveau, est clestiné a renfermer les espèces dont Ie 

 sclérenchyme est composé par trois gros spicules fusiformes et découverts. Les loges sont sub- 

 alternes, séparées entre elles, squameuses, pustuliformes avec une ouverture terminale radiée". 



Wright and Studer modify the genus as follows : — 



"The colony is branchecl, the polyps are small, with wart-like verrucae usually placed at 

 considerable intervals on the sides of the main stem and branches. The ccenenchyma is armed 

 with immense spicules in the form of either smooth or warty spindles, of which some six or 

 seven, placed side by sicle in a longitudinal manner, surround the periphery of the stem and 

 branches. These spicules often reach to a length of 1 — 3 mm., so that they are quite perceptable 

 to the unassisted eye 



"On the polyps the spicules are smaller, forming rings round their bodies. These 

 calcareous spicules are scale- or disc-like". 



For the purposes of the present work, the genus may be defined as follows: — 



Colony branched, calyces verruciform, subconical or tubular. Spicules on calyx walls 

 and tentacle bases not arranged en chevron; those of the ccenenchyma being very heavy 

 spindles, or irregular plates with their edges dentated and usually fitted as in a mosaic ; 

 those of the calyx walls smaller and sometimes scale-like and overlapping somewhat, but not 

 regularly imbricating. 



The type species of this genus is Acis guadahtpcnsis D. & M. The other known species 

 are Acis alba T. and H., A. ceylonensis T. and H., A. indica T. and H., A. nutans D. and M., 

 A. oricntalis Ridley, and A. pustulata W. and S., in addition to the three new species described 

 in this work. 



1. Acis alba Thomson and Henderson. 



Acis alba Thomson and Henderson. Ceylon Pearl Oyster Reports, Alcyonaria, 1905, p. 299. 

 Stat. 305. Mid channel in Solor Strait, of Kampong Menanga. 113 meters. Stony. 



SIBOGA-EXPEDITIE XIII <^. 6 



