EAELY PALEOZOIC BEYOZOA OF THE BALTIC PROVINCES. 217 

 STIGMATELLA CLAVIFORMIS (Ulrich). 

 Text fig. 119. 



Leptotrypa claviformis Ulrich, Geol. and Nat. Hist. Surv. Minnesota, vol. 3, 

 pt. 1, 1893, p. 319, pi. 27, figa. 20, 21. 



Among the small, massive bryozoans of the Wassalem beds are 

 rather numerous examples with a club-shaped zoarium which agrees 

 externally with the above common American form. This identifica- 

 tion is confirmed by thin sections which show practically no variation 

 in specimens from the two widely separated localities. Figures of 

 the American examples are given below. The following remarks are 

 adapted from Ulrich's description. 



Zoarium growing into simple club-shaped forms varying from the 

 smallest figured to one that is 23 mm. long and 1.5 to 2.5 mm. in 



Fig. 119.— Stigmatella claviformis. a anb &, two of the club-shaped zoarla, isrATtrEAL size; c, 



VIEW of ZOCECLA. in TANGENTIAL SECTION, X18; (f , VEKTICAL SECTION THROUGH THE MIDDLE OF A ZOA- 

 RIUM, X18. Black River (Decorah) shales, St. Paul, Minnesota. (After Ulrich.) 



diameter. Zocecial tubes growing about the axial body very much 

 as in ordinary ramose forms that grow about an imaginary center; 

 diaphragms abundant except in the outer or direct portion; walls 

 thin. Zocecial apertures subangular, nearly uniform in size, there 

 being no appreciable clusters of large cells ; without apparent arrange- 

 ment, about 14 in 3 mm. What may be mesopores, but more likely 

 are merely young zooecia, are scattered among the ordinary tubes. 

 At intervals, however, they seem to be more numerous than usual. 

 Many, perhaps the majority, of the angles of junction are thickened 

 and occupied by projecting acanthopores. 



Occurrence. — Common in the various divisions of the Black River 

 ODecorah) shales in Minnesota and Iowa ; also in the Wassalem beds 

 (D3) at Uxnorm, Esthonia (Cat. No. 57299, U.S.N.M.). 



British Museum, one specimen from Uxnorm. 



