STRUCTUEE OF ISIS HTPPURTS. 427 



From the foregoing considerations it is at once evident that 

 this jt^^enus is not only so far imperfectly described but also 

 insufficiently known to warrant its rank in a thoroughgoing 

 modern classification. It is hoped that the following observa- 

 tions may give more precision and definiteness to a species, 

 the sole representative of a distinct family. 



In the Littoral collection made by the Eoynl Indian Survey 

 Ship ' Investigator ' in the Indian Ocean are a number of 

 specimens which I have no hesitation in referring to this 

 widely distributed species. Almost all are of a light brown 

 colour, wliich in the dry condition appears as buff or ochreous- 

 yellow. In some of the specimens which have been damao-ed 

 and are apparently decayed the coenencliyma is almost white. 



As the colonies under examination present certain differences 

 inter se, and at the same time do not altogether conform to the 

 figures given by Ellis & Solander and reproduced by Lamouroux, 

 it will be useful to make a few general notes on the more typical 

 specimens, before discussing in detail the features of more 

 diagnostic importance. The following measurements were taken 

 of the height, breadth, and thickness, in centimetres : — 

 I. 9-5x8x3-5. 11.9x6x4, III. 7x0x3. IV. 10-5x4x2. 

 V. 6-5 X 7 X 4. VI. 5-5 X 4 X 4. VII. G x 4 x 3. VIIL 6x4x3. 

 In the largest and most complete specimen (PI. 43. fig. 1) 

 the branching is somewhat antler-like and is mostly confined to 

 three planes, so that the great majority of the branches are 

 directed towards one surface. The main stem is 8 millims. in 

 diameter, and about 3 centims. from the base two large branches 

 arise at slightly different levels. The sinuous nature of the 

 branches is a marked feature in this colony, the branches them- 

 selves being separated by distances of about 5 millims. The 

 secondaries and tertiaries are short, thick and cylindrical for 

 the greater part of their length, but have characteristic steep 

 conical terminations. One of the larger branches is devoid of 

 coenencliyma, and shows clearly the internodal origin of the 

 subsidiary branches, 



A second specimen, w^hich is incomplete, consists of part of a 

 main stem 6 centims. in length, from which several branches 

 arise in all directions. Of these, however, only one, which is 

 9 centims. in length, bears the terminal twigs intact. The 

 branches spring from the main stem at varying angles, about 45° 

 being the most frequent. The large complete branch curves 

 inwards towai-d the main stem and gives origin to several smaller 



