Manchester Memoirs, V oL Ixi. (igi6), No. 1. 3 



Section Scleraxonia. 



Family Bricircidrc, Sub-family Briarcma?. 



Atitliothela purvtflora, sp.n. 



Pla/e II.. Fig. 5; Plate V., Fig. 4. 



Diagnosis of Genus. — Colonies creeping or more usually 

 upright and branched. Polyps large projecting, with a calyx 

 not completely retractile. The upper part of the polyp com- 

 pletely retractile within the calyx, and the latter usually marked 

 out into eight rays or lappets. The coenenchyme of the cortex 

 with large canals, smaller canals present in the medulla. 

 Spicules : thorny spindles, spinous clubs, and rods. 



This new species is represented m the collection by three 

 colonies or parts of these. The most complete example has an 

 expanded base, from which a branch arises at a low level, which 

 divides into a larger and smaller s-econdary. The main stem 

 continues in an upward direction, and gives rise firstly to a 

 branch with a single poly]>. and then on the other side to an 

 offshoot with nine piolyps. The main axis has then three polyps 

 arranged in a tri-radiate manner around it, and then divides 

 dichotomously into two branches of equal length, the one with 

 se\'en, the other with ten polyps. The branches are not straight, 

 but are twisted or curved, and they usually come off at an angle 

 of about 4S degrees. The outer surface of the colony is fairly 

 hard and firm, and has a somewhat stony and slightly silvery 

 appearance. When the general surface of the main stem and 

 branches is examined with a lens, a granular appearance is 

 observed, which is due to the spicules. The size of the most 

 complete specimen was S6mm. in height and 50mm. in the 

 other direction. The polyps are very prominent, and the calyces 

 have eight grooves and ridges. The position of the polyps 

 relative to one another is varied owing to the curving and twist- 

 ing of the branches on which they are situated ; as a rule they do 

 not stand opposite to one another, but at one point, however, 

 three polyps originate at the same level around the stem. 



A rough transverse section through the primary shoot of 

 the colony shows a dense outer part with numerous small 

 spicules very thickly disposed, within this an area with fewer 

 spicules, and with about twenty-four canals arranged in a more 

 or less circular manner, and in the centre a part of compara- 

 tively large diameter, with long spicules and yellowish fibres, 

 surrounding a few small canals. 



The branches are approximately cylindrical, the expanded 

 base is about g by S mrn. in diameter. In the most complete 

 specimen the intervals between the branches (starting from the 

 base) are as follows: — 5 mm., 16 mm., 3 mm., 3.5 mm., g mm., 

 zj.gmm., 6 mm. The branches vary in length, the two terminal 

 branches are 4.9 mm. and 4.5 mm. The branches terminate in 



