30 



one on each internode, and between them are two minute 

 hollow denticles, which are visible only under a microscope. 

 One of these minute denticles appears to be placed on an 

 inter-articular portion placed between the extremities of the 

 internodes. The cells are small, cup-shaped, with patulous 

 unarmed apertures which are directed upwards. Tlie 

 vesicles are situated in the axillae of the branchlels, or 

 where they arise from the stem, they are pear-shaped, 

 rather small, smooth with contracted subterminal apertures. 

 In specimens washed on shore, the branchlets are commonly 

 broken off or much injured, those taken in trawl nets have 

 them about the sixth of an inch in length, while those from 

 deep water which have been brought up by tiie hook, very 

 frequently have them three quarters of an inch in length. 



PLUMULARIA. Lamark. 

 Generic Character: Plant-like, rooted, simple or branched ; 

 the shoots or offsets plumous; cells uniserial, small, sessile, 

 unilateral, usually seated in the axilla of a horny spine ; 

 vesicles scattered, unilateral. Polypes hydraform. 



The general appearance of this genus is the same as that 

 of Sertularia ; but it is distinguished from it by having only 

 one row of cells on the pinnae. 



* Stem a single tube. 

 SICKLE CORALLINE. P. Falcata. Stem waved, 



branched, alternately pinnated ; cells crowded in a single 



row, with plain apertures, lubular, slightly bulging at the 



base. 



Corallina muscosa pennata, ramulis et capillamentis fal- 

 catis, Raii, Synop. Stirp., vol. 1, p. 36, no. 16. Sickle Coral- 

 line, Ellis' Cor., p. 12, pi. 7, fig. a A, pi. 38, fig. 6. Sert. 

 falcata, Ellis and Solander's Zooph., p. 42. Turton's Lin., 

 vol. 4, p. 679. Blumenbach's Man., p. 273. Stewart's 

 Elem., vol. 2, p. 443. Plum, falcata, Fleming's Brit. An., 

 p. 546. Templeton in Mag. Nat. Hist., vol. 9, p. 466. John- 

 ston's Brit. Zooph., p. 141, pi. xviii,, figs. 1, 2. 



Hab. On shells from deep vvater, from the Eddystone to 

 the Lizard j common. 



This species rises to the height of from four to eight inches. 

 The stem is waved, slender, of equal thickness thronghout, 

 brown, smooth and divided at irregular intervals by impertect 

 septa. The branches arise somewhat irregularly, but most 

 commonly from the convex side of the waved line of the 

 stem or trunk ; and in companies of three or four. In this 

 manner it may be said that the branches arise in alternate 

 threes. They are pinnated ; the pinnae are alternate and 

 irregularly divided by imperfect septa. The cells are unila- 



