EARLY PALEOZOIC BRYOZOA OP THE BALTIC PROVINCES. 165 

 NEMATOTRYPA GRACILIS, new species. 



Text fig. 83. 



Zoarium, a cylindrical stem varying in diameter from 0.5 to 1.5 

 mm., occasionally branching dichotomously. Basal portion of zoa- 

 rium unknown, but probably attached parasitically as in RTiombo- 

 pora. Surface of zoarium smooth but with distinct maculae of small 

 mesopores at regular intervals. In young specimens the zooecia are 

 regularly oval and are arranged in distinct longitudinal rows sepa- 

 rated by rows of small, elongated mesopores. With age the longi- 

 tudinal arrangement of both sets of cells becomes less evident and 

 the zooecial apertures are less regularly oval, while the mesopores 



Fig. 83.— Nematotrypa geacilis. a, fragment of zoarium, natural size; 6, tangential section, 



X20; C, PORTION OF THE SAME, X40; d, TANGENTIAL SECTION, X50, THROUGH A MACULA AND ADJOINING 



zocecia; e, vertical section, X20; /, transverse section, X20, showing growth from central 



AXIS. KUCKEES SHALE (C2), BaRON ToLL'S ESTATE, ESTHONIA. 



assume a polygonal shape. The usual zooscium is 0.16 mm. long 

 and not more than 0.10 mm. wide, with eight or nine in 2 mm., meas- 

 uring longitudinally. The mesopores are exceptionally small, thin- 

 walled, and in practically every case isolate the zooscia. In the 

 older zoaria minute granules occur on the cell waUs, particularly in 

 the macular areas. 



It is difficult to prepare vertical sections showing the character- 

 istic central thread-like axis from which the zooecial tubes proceed, 

 but transverse sections such as shown in figure 83 /exhibit this feature 

 clearly. The noteworthy features of vertical sections are the thin- 

 walled character of the zocBcia in the immature region, the develop- 

 ment of an unusual number of small tabulated mesopores in the 

 mature zone, and the occurrence of several distinct sets of inferior 



