130 



BULLETIN 77, UNITED STATES NATIONAL MUSEUM. 



Coscinium prcenuntium, new species, likewise has a cribrose 

 zoarium and an attached base, but the zooecia are rounded and pro- 

 vided with a distinct lunarium. Internally the latter species is, of 

 course, quite different. 



Occurrence. — Ulrich's types are from the Rhinidictya bed of the 

 Black River (Decorah) shales, at Minneapolis and St. Paul, Minnesota, 

 but the species is abundant in this as well as the Stictoporella and 

 Ctenodonta beds of the same formation. In Russia specimens are 

 numerous in the Wassalem beds (D3) at Uxnorm and Gut Sack, in 

 Esthonia. 



Plesiotype.—Csit. No. 57221, U.S.N.M. 



Specimens and thin sections from the Wassalem beds at Uxnorm 

 are in the collections of the British Museum. 



STICTOPORELLA GRACILIS (Eichwald). 



Plate 7, figs. 1-3; text figs. 54, 55. 



Eschara gracilis Eichwald, Schicliteiisyst. v. Esthland, 1840, p. 205; TJrwelt von 



Rusaland, pt. 2, p. 43, pi. 1, fig. 4. 

 Micropora gracilis Eichwald, Lethsea Rossica,vol. 1, 1860, p. 393, pi. 33, fig. 4 a, 6. 



The first illustration of this species, published by Eichwald, is 

 hardly sufficient for its accurate identification, but the figures given 

 in his Lethsea Rossica refer undoubtedly to the cribrose bryozoan here 

 referred to the genus Stictoporella. This species is represented in the 

 collections before me by fragmentary examples from a number of 



localities in the 

 a /*4«^h-^.<a^ >. government of St. 



Petersburg, all of 

 them coming from 

 the Glauconite 

 limestone. The 

 most perfect of 

 these examples is 

 shown on plate 7, 

 figure 1 , where the 

 zoarium is seen 

 to be of cribrose 

 branches averaging 4 mm. in width and arising from an expanded 

 base. As usual in such forms of growth, the basal expansion and the 

 initial branches are finely striated instead of celluliferous. 



The zooecial apertures are rather large for the genus, with four in 

 2 mm., oval, and more or less oblique, with five to seven rows in the 

 width of a branch. The apertures are separated by longitudinal 

 ridges, while shallow depressions or mesopores occupy the spaces at 

 the distal end of the zooecia. As shown in figure 3 of plate 7, the mar- 

 gins of the branches are made up of the same finely striated, porous 



Fig. 54.— Stictoporella gracilis, a, Eichwald's original figure (Es- 

 chara gracilis); 6 and c copies of Eichwald's illustrations of 

 Micropora gracilis; 6, a zoarium, natural size, and c, surface of 

 same, enlarged. "Calcaire 1 Orthoceratites," Iswoss, govern- 

 ment OF St. Petersburg. 



