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CHAPTER X. 



HALYSITID^ AND TETRADIID^. 



HALYSITID7E. 



The group of the HalysitidcB constituted, in the system of 

 Milne- Edwards and Haime, a sub-family {Halysitince) of the 

 family ChcstetidcB, and it contained the five genera Halysites, 

 Syringopora^ ThecostegiteSy Chonostegites, and Fletcheria. The 

 last four of these have been already treated of; and there re- 

 mains, therefore, only the genus Halysitcs itself as the type and 

 sole representative of the family, which may be defined as com- 

 prising coralla composed of long cylindroidal tabulate corallites, 

 which are always more or less extensively united with one 

 another, but have imperforate walls, and exhibit neither mural 

 pores nor connecting-tubes. Spiniform septa may or may not 

 be present, and there may or may not be two diverse sets of 

 corallites. As the family comprises only the single genus 

 Halysites, any remarks as to its systematic position will be best 

 deferred until the characters of the genus have been discussed. 



Genus Halysites, Fischer, 1813. 



(Zoognosia, 3d ed., t. i. p. 387.) 



Catefiipora, I.amarck, Hist, des An. sans Vert., t. ii. p. 206, 1816. 



Gen. Char. — Corallum fasciculate and reticulate, composed of 

 long tubular cylindroidal corallites, which are placed side by side 

 in intersecting and anastomosing lamince or lines, any given cor- 



