1 68 W, I. RobinsoHj 



plate. There is but one species, Ptychochartocyathus laxus 

 Ludwig, from the Upper Carboniferous (Culm) of Rothmalters- 

 dorf, near Glatz, Germany. 



Original Description of the Type Species {translation). — 

 Corallum compound, hemispherical, with a concentrically striated 

 basal plate [epitheca?]. Cups deep and broad, with thick walls 

 without pores. Septa represented by twenty-four large spines 

 reaching down to the bottom of the cup. Between these, sec- 

 ondary septa (Kerbleisten) represented by rows of fine spines 

 not reaching to the base of the cup. Depth of cups 0.8 cm.; 

 breadth 0.7 cm. ; height of corallum i cm. 



The figures are very suggestive of Palaeacis but until a com- 

 parison between European and American forms is made this 

 genus may be retained. 



Genus Pleurodictyum Goldfuss. 



1826 Pleurodictyum Goldfuss. Petrif. Germ., Vol. I: 113. 



185 1 Pleurodictyum Milne-Edwards and Haime. Archiv. d. 



Mus., Vol. V: 210. 

 1856 Pleurodictyum King. Ann. Mag. Nat. Hist., Ser. 2, Vol. 



XVII: 131. 

 1863 Pleurodictyum Rominger. Ibid., Ser. 3, Vol. XI : 390 ; 



also Am. Jour. Sci., (2), Vol. XXXV 182, 84. 

 1868 Pleurodictyum Meek and Worthen. Geol. Surv. 111., Vol. 



Ill : 407. 

 1874 Michelinia (partim) Hall. 26th Ann. Rep. N. Y. State 



Mus. Nat. Hist., 1873: 113. 

 1879 Pleurodictyum Nicholson. Pal. Tab. Corals: 142. 

 1883 Pleurodictyum Roemer. Leth. Geog., Pt. I, Leth. Pal. : 428. 

 1888 Pleurodictyum Herrick. Bull. Denison Univ., Vol. 



HI: 30. 

 1891 Pleurodictyum Beecher. Trans. Conn. Acad., Vol. VIII, 



Pt. 2: 211. 



The early descriptions are not satisfactory, as the structure 

 of the genus was not understood. The following description is 

 given in Zittel-Eastman (1913: 114) : 



"Corallum depressed, discoidal, circular or eUiptical in con- 

 tour, lower surface covered with concentrically striated epitheca, 

 and frequently a foreign vermiform body occupying the center 



