BRYOZOA. 677 



near the surface, of a dark ring of tissue immediately surround- 

 ing the cavities and a central lucid region (see fig. 3a) . Meso- 

 pores few, generally small, situated mainly at the angles, often 

 wanting over considerable spaces. A few small acanthopores 

 present. Apertures angular or sub-circular, subequal, arranged 

 in moderately regular curved rows, about 0.15 mm. in diameter, 

 with nine in 2 mm. 



The position of this species is doubtful. In many respects the 

 Silurian genus Leptotrvpa is suggested, but the presence of 

 mesopores, argues against a reference to that genus. The 

 mesopores again are sometimes arranged as in Cyclopora fungia, 

 but the primitive portion of the zooecia and the structure of 

 their walls is different. The majority of the characters known 

 point to the TREPOSTOMATA rather than to the CRYPTOSTOMATA, 

 but till more material can be studied it has been deemed best 

 to arrange the species as above. 



Care must be exercised in separating the species from the 

 laminar form of Stenopora tuberculata Prout, which occurs 

 abundantly at the same locality. When the lower surface alone 

 is visible, thin sections are generally required to distinguish 

 them. They, of course, do so effectually. 



Position and locality: Keokuk group. Warsaw, 111., Greene 

 Co., 111., and Bentonsport, Iowa. 



