The Relationship of the Tetracoralla to the Hexacoralla. 163 



Palccacis, Microcyathus, and Ptychochartocyathus belong in 

 this group, having the same kind of thick walls and interlacing 

 canals with pores opening on the inner cavity. The same laws 

 of budding apply to them, except that in the case of P. cunei- 

 f or mis the addition of buds is vertical instead of radial. 



It is here proposed to place these closely related genera, 

 Palcracis, Microcyathus, and Ptychochartocyathus, in one family, 

 Leptoporidas. This name was used in 1892 by Miller for a 

 family which contained the one genus Leptopora and which was 

 placed doubtfully with the Tabulata. As the family was not 

 defined, a definition may be formulated which will include the 

 other closely related genera, as follows: 



Phylum Coelenterata. 



Sub-phylum Cnidaria. 



Class Anthozoa. 



?Sub-class Tabulata (of uncertain relationship). 



Family Leptoporidas Miller. 



Leptoporidae : Specialized Tabulata with large corallites. 

 Tabulse much modified or wanting. No true septa or true mural 

 pores. Walls thick; traversed by canals. Inner wall grooved, 

 ridged, or occupied by irregularly spaced pores which are the 

 openings of the canals. 



Genus Leptopora Winchell. 



1864 Leptopora Winchell. Proc. Acad. Nat. Sci. Phila., Vol. 



XV, 1863 : 2. 

 1888 Cleistopora Nicholson. Geol. Mag., Dec. Ill, Vol. V: 



150-152. 



Original Description of Leptopora. — -"Corallum occurring in 

 thin discoidal masses; cells very shallow, crowded, polygonal, 

 separated by a common cell wall, which is vertically striated; 

 interior of cells filled with a finely vesicular tissue ; cups polyg- 

 onal, concave, elevated in the center, and displaying numerous 

 radial lamellae." 



Original Description of Cleistopora. — "Corallum small, discoid, 

 usually attached by its entire base to foreign bodies. Corallites 

 short, prismatic, without tabulae, and having the inferior portion 

 of the visceral chamber completely filled up with loosely reticu- 



