244 



BULLETIN 11, tTNITED STATES NATIONAL MUSEUM. 



sional shallow depressions between the zooecial apertures. True 

 acanthopores probably wanting, but small knots at the angles of 

 junction may be noticed. 



Eridotrypa sedilis may be distinguished from associated ramose 

 bryozoans by its slender, cyhndrical, infrequently dividing, smooth 

 branches, with more or less oblique apertures and thick walls or inter- 

 apertural spaces. 



Occurrence. — ^Very abundant in the Wesenberg beds (E) at Wesen- 

 berg (Cat. No. 44827, U.S.N.M.). Less common in the Jewe lime- 



PiG. 138. — Ekidoteypa ^dilis. Copies of Ulrich's figures of Eridotrypa mutabilis. a, specimen 

 of average size; b, surface of another example, x18, exhibiting a macula and neighboring 

 zoqecia; c, tangential sections, x18, representing the mature condition; d, a zocecium of the 

 same section, x50; e, vertical section, x18, of a mature example with an incrusting layer 

 op zocecia growing in the opposite direction. lower part of trenton limestone, goodhue 

 County, Minnesota. 



stone (Dl), Baron Toll's estate (Cat. No. 57316, U.S.N.M.); in the 

 Kegel limestone (D2), at Kegel (Cat. No. 57317, U.S.N.M.); and in 

 the Wassalem beds (D3), at Uxnorm, Esthonia (Cat. No. 57315, 

 U.S.N.M.). In America the species is abundant in Black River and 

 Trenton strata at localities too numerous to mention. The speci- 

 mens figured by Eichwald and Dybowski were derived from the 

 Wesenberg beds at Wesenberg, while Ulrich's type-specimen came 

 from the lower Trenton shales at Cannon Falls, Minnesota. 



British Museum, three specimens and one thin section from Rus- 

 sian localities. 



