118 THE PALEONTOLOGY OF MINNESOTA. „ ^ „ „ 



[Stomatopora. 



circular, direct, with a peristome, about 0.09 mm. in diameter, situated near the ante- 

 rior end. Mural perforations minute and but rarely preserved. 



In the Trenton or typical form of this species the zooecia, as a rule, are less swol- 

 len and the adnate zoarium divides less frequently than in the better known Cincin- 

 nati form. In the latter, therefore, the network is closer, and occasionally the 

 growth is so luxuriant that the rows cross each other to such an extent that but 

 little space is left between the cells. No distinction, however, can be based upon 

 these characters since, when good series of specimens are studied, it is found that 

 among those from Trenton localities some have more than commonly swollen and 

 crowded cells, while in some of those from the geologically higher localities the 

 growth is lax and the zooecia comparatively narrow. 



Formation and locality.— TtQuton group, at Trenton Falls, N6w York ; Ottawa, Canada; Cannon 

 Falls, and other localities in Minnesota where the upper third of the Trenton shales are exposed ; Hudson 

 Biver group at Cincinnati, Ohio, (350 to 425 feet above low water mark in the Ohio river), and in the upper 

 beds at Bichmond, Indiana ; Wilmington and Savannah, Illinois, and other localities. 



Mus. Reg. Nos. 5924, 8045. ^ 



Stomatopora tuegida Ulrich. 



PLATE I, PIGS. 23 and 23. 



Stomatopora turgida Ulrich, 1890. Jour. Cin. Soc. Nat. Hist., vol. xii, p. 176. 



Original description.— " ZoSbrinm adnate, consisting of a single branching series of 

 zooecia. Zooecia comparatively very large, the anterior half much swollen, rapidly 

 tapering posteriorly, with the slender, tubular proximal end inserted beneath the 

 turgid anterior end of the preceding zooecium. Five zooecia in 5 mm.; length of 

 each zooecium varying from 0.85 to 1.30 mm.; the greatest diameter of the anterior 

 half from 0.4 to 0.6 mm. The longest cells are the least turgid, while the shortest 

 are the most. Apertures round, bordered by an elevated margin, small, 0.1 mm. in 

 diameter, and situated about one-fourth of the length of the zoeocium from its ante- 

 rior end. 



" I have a number of specimens of this species, and all consist of comparatively 

 few zooecia. Nor do the series of cells in any of them branch often ; from which it 

 appears that the production of two " gemS " was a much less frequent occurrence 

 than in the related S. inflata Hall. S. turgida is further distinguished from that and 

 all other species of the genus known to me, by the much larger zooecia." 



Formation and locality.— JJpTper beds of the Hudson Kiver group at Wilmington, Illinois. 



