EAELY PALEOZOIC BRYOZOA OP THE BALTIC PROVINCES. 323 



the ordinary large openings are in reality true mesopores and not 

 young zooecia. A vertical fracture or thin section brings out more 

 obvious differences, as a comparison of figures 191 and 200 will 

 indicate. Most important of these differences are the strongly 

 beaded mesopores and the straight zooecial walls of D. liennigi in 

 contrast with the strongly crinkled walls and absence of mesopores 

 in the Monotrypa. The zoarium of Diplotrypa liennigi is of smooth, 

 rounded masses composed of thin walled, polygonal zooecia with 

 occasional small, angular mesopores. Six of the ordinary zooecia in 

 2 mm. Acanthopores wanting. The specific characters are best 

 shown in , vertical sections, where the slightly undulated zooecial 

 walls, the decided beading of the mesopores, and the paucity of 

 diaphragms in the zooecia proper are most diagnostic. 



The specific name is in honor of Dr. Anders Hennig, of Lund, 

 Sweden, in appreciation of his work upon the Silurian Bryozoa of the 

 island of Gothland. 



Occurrence. — Apparently rare in the Kuckers shale (C2), Baron 

 Toll's estate, near Reval, Esthonia. 



Eolotype.—C3it. No. 57414, U.S.N.M. 



Thin sections of the type-specimen are in the collections of the 

 British Museum. 



DIPLOTRYPA WESTONI Ulrich. 



Text fig. 201. 



Diplotrypa westoni Ulrich, Contr. Micro-PaL Cambro-Sil., Pt. 2, 1889, p. 30, 

 pL 8, figs. 4-46; Zittel's Textbook of Paleontology (Eng. ed.), 1896, p. 274, 

 fig. 457.— Whiteaves, Pal. Foss., vol. 3, pt. 3, 1897, p. 163. 



Several specimens of Diplotrypa from the Chasmops limestone of 

 Sweden were at first assigned by me to a new species, but upon 

 close comparison I find that the differences between them and the type 

 of Diplotrypa westoni are too slight even for varietal distinction. The 

 characters of the Swedish examples are shown in the accompanying 

 figures. The size of the zooecium, number of mesopores, and distri- 

 bution of diaphragms in both sets of tubes is practically the same. 

 Indeed, the only difference that I can point out between Ulrich's 

 figures and my own is the slightly greater number of mesopores in 

 the latter, a distinction removed by other specimens. 



Diplotrypa westoni need only be compared with D. petropolitana, 

 but the more abundant diaphragms of the latter easily separate the 

 two, although other differences can be seen by comparing their 

 respective figures. The distinctive characters of D. westoni are best 

 exhibited in vertical sections. Here the sparse tabulation of the 

 zooecia is most evident, but a second striking feature is the angularity 

 of the beading formed by the walls of the mesopores. In most 



