58 



BULLETIN 77, UNITED STATES NATIONAL MUSEUM. 



As noted in the general remarks upon the Ctenostomata, the refer- 

 ence of these fossil forms to that order seems the best arrangement 

 under the circumstances. In the case of the present species particu- 

 larly its unquestionable reference to the Bryozoa must be substan- 

 tiated by future discoveries. 



d 



Fig. 6.— Hetekojtema pbiscum. a, a colony attached to a Valve of Obolus, X4; &, a poetion 



OF THE SAME, X20, n>LUSTEATING THE METHOD OF BRANCHING; C, PARTS OF TWO COLONIES, X35, AVITH 

 one growing over another; (Z, small portion of ANOTHER ZOARIUM, X50, SHOWING THE MICRO- 

 SCOPIC STRUCTURE OF THE THREADS. TJNGULITE SANDSTONE (A2), UPPER CAMBRIAN, JEGELECHT 



Falls, Esthonia. 



Occurrence. — An abundant species in the Upper Cambrian (Ungu- 

 Hte) sandstone (A2) at Jegelecht Falls, Esthonia. 

 Coty pes. —Cat. No. 57180, U.S.N.M. 

 British Museum collections, one specimen. 



Order CYCLOSTOMATA Busk. 



The bryozoans belonging to this order have a simplicity of struc- 

 ture highly characteristic in both zoaria and zooecia. The zooecia are 

 especially simple throughout the order, so that the classification is 

 based almost entirely upon their arrangement and method of growth. 

 The recent forms show that this same simplicity extends to the poly- 

 pide, and that the larvae of the different families are practically 

 identical. The zooecia are simple, calcareous tubules with plain, 

 uncontracted, usually rounded apertures and with minutely porous 

 walls. The interzooecial spaces may or may not be filled with sohd 

 strengthening deposits. Marsupia and appendicular organs are want- 

 ing, but the ovicell is present in the form of a large cell or an inflation 

 of the zoarial surface set aside for reproductive purposes, 



The simplest Cyclostomata are comprised in Busk's families Diasto- 

 poridse and Idmoneidse and in the Entalophoridse of Reuss, all of 

 which have numerous fossil species. Each of these families is rep- 



