EARLY PALEOZOIC BEYOZOA OF THE BALTIC PROVINCES, 209 



like cells on the flat side of the HyolitJies, and the restriction of the 

 thin-walled, ordinary zooecia to the curved portions of the shell. 

 A vertical section of this region of small cells is shown in the lower 

 half of figure 114 c, and a tangential view in figure 114 d. Ordinary 



Fig. 113.— Leptotetpa hexagonalis. a, tangential section of the American type op the species, 



X20; THE LAEGER ZOOECIA FORM PART OF A MACULA, WHILE THE MORE NUMEROUS, SMALLER CELLS ARE 

 OF THE ORDINARY INTERMACULAR KIND; &, SEVERAL ZOCECIA OF THE SAME SECTION, X30, SHOWING 

 THEIR SEHPLiaTY OF STRUCTURE; C, VERTICAL SECTION, X20, EXHIBITING BOTH REGIONS OF THE THIN 

 ZOARIAL LAYER. MIDDLE OEDOVICIAN (PLATTEVILLE) LIMESTONE, MlNEEAL POINT, WISCONSIN. 



zooBcia are wanting entirely in this area which undoubtedly repre- 

 sents similar thickwalled, mesopored areas at the base of the zoa- 

 rium in such forms as Diplotrypa Mcornis. The subject of such areas 

 of small cells is discussed on a previous page, where it is suggested 



Fig. 114.— Leptotrypa hexagonalis. a, tangentiae section, X20, op a Russian example; 6, ver- 

 tical SECTION, X20; C, A vertical section, X20, PASSING THROUGH A LAYER OF ORDINAEY ZOCECU, 

 AND ALSO CUTTING THE CLOSELY TABULATED, MESOPORE-LIKE TUBES GROWING UPON THE FLAT SIDE OP 

 THE shell; d, TANGENTIAL SECTION, X20, THEOUGH THE SMALL, THICK-WALLED CELLS. KUCKEES SHALE 



(C2), Baron Toll's estate, Esthonxa. 



that the HyolitJies shell frequently or invariably rested upon its flat 

 side in the mud of the sea bottom. 



The internal structure is so simple that specific mention of it is 

 hardly necessary. The strong acanthopores spoken of in the original 



