112 BULLETIN 11, UNITED STATES NATIONAL MUSEUM. 



the basal membrane or epitheca forming the wall of this tube, and 

 to proceed to the surface in a gentle curve. In the immature region 

 their walls are thin and diaphragms are absent. In the mature zone 

 the walls thicken, interzooecial spaces are developed, and an occasional 

 diaphragm is inserted. In well-developed species of CMlotrypa the 

 interzooecial spaces are filled with vesicles precisely as in Fistulipora, 

 but in the present form the vesicles are almost entirely absent and 

 their place is occupied by laminated tissue similar to that occurring 

 in the more primitive Ceramoporidae. Tangential sections exhibit 

 elongate oval zooecia with a slight lunarial thickening at the proximal 

 end. 



The delicate cylindrical branches with a small, central axial tube, 

 and small, elongate apertures arranged in ascending spirals, are 

 different enough from all other bryozoans to require no comparisons. 

 While the species has some resemblance to Ccdoclema, it is believed 

 that the majority of its characters show it to be a primitive form of 

 CMlotrypa. 



Occurrence. — Apparently rare in the Lyckholm limestone (Fl) at 

 Kertel, island of Dago. 



Holotype.—Csit. No. 57209, U.S.N.M. 



British Museum, thin sections of type-specimen. 



Order CRYPTOSTOMATA Vine. 



This order of the Bryozoa was proposed by Vine in 1883 as a sub- 

 order to include mainly the bifoHate ptilodictyoid genera. Since 

 that time the detailed studies of Ulrich have extended the Umits 

 of the order so that it now embraces such families as the FenesteUidse 

 and Acanthocladiidse, in addition to the Ptilodictyonidse and related 

 famines. A concise definition of the order has been given by Ulrich 

 in the English edition of Zittel's Textbook of Paleontology. This is 

 as follows: 



Primitive zooecium short, pyriform to oblong, quadrate, or hexagonal, sometimes 

 tubular, the aperture anterior. In the mature colony the aperture is concealed, 

 occurring at the bottom of a tubular shaft ("vestibule"), which may be intersected 

 by straight diaphragms or hemisepta, owing to the direct superimposition of layers 

 of polypides. Vestibular shaft surrounded by vesicular tissue, or by a solid calcareous 

 deposit; the external orifice rounded. Marsupia and avicularia wanting. 



Comparing the Cryptostomata with the other orders of Bryozoa, 

 it is found to be most closely related to the Chilostomata ; in fact, the 

 cryptostomatous bryozoans are probably only the Paleozoic repre- 

 sentatives of the Chilostomata so abundant in Mesozoic, Cenozoic, 

 and recent times. As pointed out by Ulrich, the Cryptostomata 

 differ, however, first, in having neither marsupia nor avicularia; 

 second, in the much greater deposit of calcareous matter upon the 

 front of the zooecia, thus producing the vestibule; third, in that 



