EAELY PALEOZOIC BEYOZOA OP THE BALTIC PEOVINCES. 



77 



CERA.MOPORA SPONGIOSA, new species. 



Text fig. 19. 



Zoarium a small, explanate mass several centimeters in diameter 

 and less than 5 mm, thick. Celluliferous surface smooth; noncellu- 

 liferous basal side lined with a strongly wrinkled epitheca. The 

 maculse in young expansions are small, slightly depressed areas from 

 which the zooecia radiate; in old examples they are represented by 

 clusters of irregular, thick-walled mesopores. Zooecia large, 4 to 5 in 2 

 mm., irregularly polygonal in outline, with occasional mesopores. 

 Walls of both zooecia and mesopores irregular in shape and thickness. 



mini// 





I 





A 



Fig. 19.— Ceramopoea spongiosa. a, portion of a zoarium, natural size, showing concentric 



RINGS OP epitheca; 6 AND C, TANGENTIAL SECTION, X9, AND PORTION OF SAME, X20, SHOWING THE 

 NUMEROUS CONNECTING PORES; d, TANGENTIAL SECTION OF THREE ZOCECIA, X20, EXHTBITrNG STRUCTURE 

 OF "WALLS AND OF THE LUNARIUM; e AND/, VERTICAL SECTIONS, X9 AND X20, "WITH TABULATION AND 

 CONNECTING PORES. WASSALEM BEDS (D3), UXNORM, ESTHONIA. 



>' 



Lunarium of considerable size but so irregular in old specimens that 

 it can hardly be separated from the equally irregular zooecial wall. 

 In young examples the relations of the zooecia, mesopores, and lunaria 

 are more clearly shown. Here the zooecium is more rounded and has 

 a distinct, slightly elevated, hood-shaped lunarium overarching the 

 proximal fourth of the zooecial cavity. Mesopores are represented in 

 such specimens by shallow pit-like depressions just behind the 

 lunarium. 



While a considerable variation is shown at the surface of speci- 

 mens according to their age, the internal characters of the species 



