822 



BULLETIN 11, UNITED STATES NATIONAL MUSEUM. 



is more marked in the Russian species, which may be defined as 

 follows : 



Zoarium a dome-shaped or hemispheric mass about 20 mm. wide 

 and 12 mm. high. Surface smooth, maculae inconspicuous, and dis- 

 tinguished mainly by the presence of more numerous mesopores. 

 ZocBcia polygonal, irregularly arranged, three to four in a space of 2 

 mm. Mesopores of irregular sizes and shapes and seldom completely 

 isolating the zooecia. Walls of both zooecia and mesopores thin. 



In vertical sections the very irregular zooecial walls are the most 

 striking feature, and this peculiarity alone will aid considerably in the 

 identification of the species. The difference in tabulation between 

 zooecia and mesopores is often so slight that the latter can only be 

 recognized by their smaller size. In many cases the mesopores 

 abruptly cease and their places are taken by zooecia of normal size. 



Fig. 200.— Diploteypa hennigi. a, side view of a zoakium, natural size; 6, tangential section, 



X20; C, VERTICAL SECTION, X20, SHOWING THE ZOCECIAL WALLS BUT SLIGHTLY UNDULATING ALTHOUGH 

 THE MESOPORES ARE STRONGLY BEADED. KUCKEES SHALE (C2), BARON TOLL'S ESTATE, EsTHONIA. 



Compared with other hemispheric bryozoans, the polygonal 

 zooecia and mesopores, with their crinlded walls and the uniform dis- 

 tribution of diaphragms, are diagnostic of Diplotrypa moniliformis. 



Occurrence. — Apparently rare in the Jewe limestone (Dl), Baron 

 Toll's estate, near Jewe, Esthonia. 



Holotype.—C&t. No. 57413, U.S.N.M. 



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

 British Museum. 



DIPLOTRYPA HENNIGI, new species. 

 Text fig. 200. 



Externally this species has much resemblance to the associated 

 Monotrypa jewensis, but close examination will show that its zooecia 

 are smaller, and that the small polygonal apertures scattered among 



