or Little Known, Polyzoa. 107 



avicularia are scattered irregularly over the back, sometimes 

 with triangular mandibles, and occasionally one of the latter 

 of a large size is found at the base of a fenestra. 



In young cells there are frequently two long, hollow, 

 jointed spines articulated at the upper margin of the mouth. 

 In older cells, and occasionally in younger ones, there is an 

 enormous spine on one side articulated to an elevation of 

 the peristome. These spines are of peculiar structure (as 

 pointed out by Hincks), consisting of segments narrower at 

 the base, expanding upwards, and each segment fitting into 

 the one below somewhat like the joints of an Equisetuin. 



Variety sinuata. 



Polyzoarymuch convoluted and contorted, thick. Fenestras 

 rounded, narrower than the interspaces. Mouth with a 

 deep and wide sinus in the lower lip, on one angle of which 

 is a large oval avicularium. Ovicell prominent, the vertical 

 band thickened and frequently, especially in older cells, 

 slightly elevated. Back vibicate, dense, granular. 



This variety, which attains a size of about 2 inches by 

 1 to 1J, is usually found surrounding the narrow stems of 

 black algge. The polyzoary is much thicker and denser than 

 in the normal form. The sinus in the lower lip is much 

 wider and deeper, and the oral avicularium is larger. The 

 jointed spines, which are commonly present, are of great 

 size; the lower joint is very long, the succeeding much 

 shorter. The ovicells are broader, and the vertical beaded 

 line is frequently elevated towards its upper extremity. 

 The avicularia are usually very numerous, and are often 

 raised on calcareous eminences. They vary much in shape, 

 and are frequently broadly spatulate. The back is densely 

 granular, the vibices little prominent, and the avicularia very 

 few. 



R. monilifera, form umbonata. 



Polyzoary foliaceous, expanded, or convoluted. Fenestras 

 elliptical, narrower than the interspaces. Cells quadrate or 

 ovate, those towards the edges separated by much-raised 

 margins, surface granular, glassy. Mouth sloping obliquely 

 backwards; in young cells lower lip nearly straight or 



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