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a solid axis. Hicksou does not seem to be convinced as to this character, but 

 among our present specimens we can clearly distinguish (1) forms without an 

 axis and (2) forms with an axis. 



The mode of branching and the extent to which tube-forming has developed 

 do not in our opinion constitute a specific character. Hickson also holds this 

 view, so that we are surprised at his species, .S'. ramosa, where the only diagnostic 

 feature seems to be the tunnel-like expansions. He says : " The spicules of the 

 axis and of the branches are so remarkably similar to those of the other species 

 that I cannot distinguish them ". The degree of retractility of the anthocodise 

 is also a matter of little importance. 



The size and grouping of the verrucfe are of no diagnostic value. The 

 descriptions given below of the various specimens prove this point conclusively. 



The architecture of the anthocodice may, however, be regarded as giving at 

 least a hint to the species. We have studied this in some detail and the 

 results are on the whole satisfactory. A more extended study of other speci- 

 mens is necessary, however, before any definite suggestions may be made. 



All the specimens in the present collection are referred to two species, viz., 

 S. tortuosum and S. sterroklonium. In S. tortuosum there is no hint of an axis, 

 and the characteristic spicules are Y-shaped and irregular. (2) In (S'. sterrok- 

 loninm there is a distinct fusion of spicules to form an axis and the spicules 

 include spheres. 



We incline strongly to Hickson's opinion that ,S'. tabulosum, S. grayi, 

 and S. cervicornis should all be referred to S. tortiiosmn. 



Solenocaulon tortuosum (Gray). 



A. The largest specimen of this species occurs in the Wood-Mason Collec- 

 tion ; it is 260 mm. in height. The basal portion or trunk occupies about 80 

 mm., and has evidently been embedded in mud ; it is slightly expanded at 

 the extremity. The main stem or stalk is tubular in several places while the 

 branches are nearly all tubular throughout. The diameter of the trunk is 

 8 mm. and the stalk at its widest part is 10 mm. There is only a trace of 

 gutter-like structure on the secondary branches. The verrucse are small and 

 dome-like ; the anthocodife are almost completely retracted. The polyps are 

 disposed almost exclusively in a single row both on the main stalk and on the 

 margins of the flattened secondary branches. The colour of the colony ap- 

 proaches brick-red but the anthocodiis are white. 



B. Several damaged specimens evidently belonging to two colonies of which 

 the trunks have become detached. The stalk-portion of one colony is 100 mm. 

 in length while the detached trunk is 65 mm. The diameter of the trunk is 4 

 mm., that of the colony is 6 mm. The whole of the stalk is cylindrical, and at 



