New Lower Silurian Bryozoa. 



STOMATOPORA TENUISSIMA, n. sp. 



175 



Fig. ■l.—Stornatopera tenuissima, n. sp. and S. proutana, Miller, a, portion of zoarium 

 ■of S. tenuissima, x7, showing its slender zooecia and mode of growth ; b, several 

 zooecia of same magnified eighteen diameters, to show their apertures and form more 

 clearly, c, several zooecia of one of the most slender examples of S. proutana seen. 

 Introduced for comparision. 



Zoarium adnate, consisting of frequently branching uniserially 

 arranged zocecia. Zocecia exceedingly slender, about seven in 

 eight mms., each from 1.0 to 1.5 mm. long, usually increasing 

 very gradually from the proximal end, where the diameter is 

 about 0.04 mm., to near the slightly bulbous anterior or upper end, 

 which varies from o. 11 to 0.18 mm. in diameter. Aperture cir- 

 cular, small, about 0.05 mm. in diameter, situated very near the 

 anterior end of the zocecium. 



This and S. turgida illustrate the extremes of difference in shape 

 and size of the zocecia of Stomatopora so far noticed. 6*. tenuissima 

 is closely related to S. proutana, Miller, but its zocecia are much 

 longer. Miller's species, with scarcely any modification, ranges 

 from low in the Trenton (Birdseye limestone) to the top of the 

 Cincinnati group. 



Position and locality : Toward the top of the Utica horizon of 



