106 



Plumvlaria falcata ; on which it is very frequently abundant. 

 It is a small calcareous species and generally of a purple or 

 purplish white colour. It grows on a narrow base, is creep- 

 ing, and dichotomously branched in a revolute manner. The 

 cells or tubes arise from the upper surface only, the lower 

 being plain or only striated from the position of the cells 

 above ; they rise in two rows from near the centre of each 

 branch and diverge towards the sides, leaving a central 

 groove which runs through ail the branches and gives the 

 potypidom a remarkable and characteristic appearance. 

 The tubes are very prominent, and occasionally distant, with 

 plain rouud apertures. 



If a specimen grows in an unfavourable situation, it will 

 sometimes be curiously distorted. I have specimens which 

 have grown in the crevices of stones in which the branches 

 have been so closely pressed together that they seemed, at 

 first view, as if united into one mass; but an examination soon 

 discovered the branches and the two rows of lubes. In 

 others there have been no branches and the polypidonis have 

 had a simple flat surface, but the peculiar leaning of the 

 tubes was present in all. It varies in length from one quarter 

 to half-an-inch in length; but on one occasion it attained 

 three quarters of an inch and was the largest I ever saw. 



TUBUL1PORA PBALANGEA. Encrusting; poly- 

 pidonis divided into from two to five lobes; tubes 

 divergent from a central line running through the centre. 

 PI. xix., fig. 8. 



Hab. On stones and the wicker work of crab pots, in 

 from ten to twenty fathoms water, common. 



This species in its most simple state resembles a deformed 

 condition of Tubu/ipora serpens, with which it has hitherto 

 been confounded. Having examined a great number of 

 specimens from different localities, growing under different 

 circumstances, I am induced, now, to consider them as 

 distinct. It is encrusting, circumscribed, oval, and the oval 

 is divided at the margins into from two to five lobes or 

 festoons. Through the centre of each lobe runs a line or 

 depression, from which the tubes diverge on either side as 

 in Tubulipora serpens. The tubes are comparatively long, 

 and are not in contact with each other as viewed from above. 

 They are numerous and arranged in perpendicular rows ; 

 each row is formed of a single series of tubes, which are in 

 contact with each other; each being united to the one above 

 and below. This arrangement presents the appearance of a 

 number of Pan's pipes placed perpendicularly, the sets 

 being separated from each other. 



