EABLY PALEOZOIC BRYOZOA OF THE BALTIC PROVINCES. 133 



that the specimens so designated were only young examples. Curi- 

 ously enough, most of the specimens found in the Baltic strata are 

 a number of examples from the Wassalem beds at Uxnorm, differing 

 in no appreciable manner from the types of the variety minor. It 

 is probable that this is only an accidental coincidence, and that in 

 the course- of time specimens of the more mature typical form of the 

 species will be discovered. The surface characters of both the type 

 form of the species and of the young examples designated variety 

 minor are illustrated in the accompanying figures. The species is 

 described in considerable detail by Ulrich, but it is believed that the 

 narrow, bifoliate, ribbon-like stipes bearing longitudinal rows of 

 somewhat elongated quadrate zooecia, with granulose separating 

 ridges, are sufficient to distinguish it from most associated bryozoans. 



Fig. 57. — Rhtnidictta exserta. a and b, two typical fragments, nattjral size; c, tangential sec- 

 tion, X20, THROUGH mature ZONE OF AN OLD EXAMPLE; d, VERTICAL SECTION, X20, OF THE SA3IE SPECI- 

 MEN. Wesenberg limestone (E), Wesenberg, Esthonia. 



The internal structure is very similar to Ehinidictya exserta, illustrated 

 above. Comparisons between the two are given on page 134. 



Occurrence. — ^Very abundant in all the divisions of the Black River 

 (Decorah) shales, and in the Fusispira and Nematopora beds of the* 

 lower Trenton limestones of Minnesota and Iowa; common in the 

 Wassalem beds (D3) at Uxnorm, Esthonia (Cat. No. 57227, U.S.N.M.)' 



One specimen (forma minor) from the Wassalem beds at Uxnorm 

 in the collections of the British Museum. 



RHINIDICTYA EXSERTA (Eichwald). 



Text figs. 57, 58. 



Eschara exserta Eichwald, Urwelt Russlands, pt. 2, 1847, pi. 1. fig. 2. 

 Stictopora exserta Eichwald, Lethsea Rossica, vol. 1, 1860, p. 392, pi. 26, fig. 11 a, b. 



As shown in figure 58, the two illustrations of Stictopora exserta 

 given by Eichwald seem to represent the surface of quite different 

 bryozoans. I am unable to find any form corresponding to figure 



