THE BRYOZOA BASSLER. 



365 



tures. The Cheilostomata exhibit the highest type of development 

 in the bryozoa and for that reason the description of the various 

 functions of the animal has been reserved for this place. The living 

 bryozoan shows that these functions in the order of their impor- 

 tance are first those dealing with reproduction, namely, with the 



26 



■MM 



MM 



29 



,20 



Fig. 8. — Cryptostomata. 



1-2. EscMropora subrecta Ulrich. Middle Ordovician (Black River) shales of Minne- 

 sota. A typical member of the Cryptostomata. 1. The narrow bifoliate zoarium, 

 two-thirds natural size, with a pointed striated base which fits into a corresponding 

 socket attached to other objects. 2. Surface of the basal part of a specimen, X6. 



3-4. Arthrocl-rma billingsl Ulrich. Ordovician (Trenton) limestone, Ottawa, Canada. 

 3. Zoarium composed of numerous joints articulating with each other, two-thirds 

 natural size. 4. A single joint or segment, Xl2, of a related species (A. cornutum 

 Ulrich) with a socket for articulation on top and the pointed basal articulating 

 process at the bottom. 



5. A threadlike bryozoan of this order (Ncmatopora ovalis Ulrich) natural size and 

 X12, from the Middle Ordovician shales of Minnesota. 



