SYSTEMATIC ACCOUNT 239 



of preserved zooids — dorsal side of body and stolon light brown, ventral side brownish 

 white. Proboscis with dark brown upper and lower edges. Usually eight pairs of arms, 

 each with two black longitudinal bands running along the entire length as in C. nigrescens. 

 No end-swellings with refractive beads. Female and hermaphrodite zooids found in the 

 same colony. Up to ten buds on each zooid. The colony has a smoky grey colour which 

 suggested the specific name. 



Locality. 



St. 170. 23. ii. 27. Off Cape Bowles, Clarence Island, 61° 25' 30" S, 53° 46' 00" W. Gear DLH. 

 342 m. One entire colony and a broken piece. 



The material of this species consists of a single large colony, and another broken piece 

 from which the zooids were removed and separately preserved. Sections were made of 

 the preserved zooids and the large colony was used only for purposes of general 

 description. 



The large colony is flat and semicircular in shape, but since the diametrical edge is 

 irregular and broken, it may be assumed that an entire colony is oval or circular with a 

 convex upper surface, thick in the centre and thin towards the edge (PI. XXXIV, fig. i). 



In most other species of Cephalodisciis the colony is formed by the secretion of 

 coenoecial substance, the inclusion of sand grains being only a secondary factor de- 

 pending on the nature of the surroundings. In C. solidus (Ridewood, 19 18 6, p. 18) 

 large quantities of sand grains, sponge spicules and diatoms are found in the common 

 coenoecial substance of some of the colonies, while others are leathery and non- 

 arenaceous. In C. agglutinans foreign particles are included in the soft substance, but 

 some parts of the branches may be devoid of sand grains. In C.fiimosus the entire mass 

 of the colony is formed of a dense agglutination of sand grains. The particles are very 

 minute and of uniform size and being closely packed together give a homogeneous 

 appearance to the colony. The coenoecial substance is sparsely secreted and is used 

 only for making the thin-walled tubes and binding the sand grains together. Since the 

 bulk of the colony is formed of such a consolidation of sand particles, it is very brittle 

 and easily breaks to pieces when removed from its place of attachment. The basal part 

 has an irregular surface, because the colony grows on a sandy bottom, to which it is 

 fixed by the secretion of a thin layer of coenoecial substance. When the colony is 

 dislodged large particles of the substratum firmly attached to the basal surface come 

 with it. It seems clear from the nature of the particles that they must definitely be 

 selected by the zooids for the construction of the coenoecium, in the same way as certain 

 Foraminifera construct their arenaceous shells. Ridewood (191 8 o, p. 41) observed that 

 the inclusion of sand grains or foreign particles is not a constant character of any species 

 of Cephalodisciis, and that it may be purely local, depending only on the nature of the 

 sea bottom where the zooids first settled down. " It is quite possible that in more rocky 

 parts of the ocean floor the zooids of the species might build up a perfectly clear and 

 transparent coenoecium." Though this is applicable to most species of Cephalodiscus, 

 it cannot be said that the arenaceous nature of the colony of C. fumosus depends on 



