138 



NORTH AMERICAN INDEX FOSSILS. 



phragms remote; no mesopores or acanthopores ; mature and 

 immature regions indistinguishable. Ord.-Sil. 



74. M. tabulata (Hall). (Fig. 191, a-c.) Lower Devonic. 

 Spheroidal or hemispheric; tubes polygonal, with thin and 



strongly corrugated walls, the corrugations forming nodes at the 

 angles. 



Helderberg (Coeymans and Port Ewen) of New York, etc. 



75. M. ? amplectens Grabau. (Fig. 192 a-d.) Devonic. 

 Encrusting brachiopod shells, generally large Spirifers on which 



species of Aulopora have grown. The openings of the Aulopora 



Fig. 192. Monotrypa amplectens. a, encrusting Spirifer shell to which are attached 

 tubes of Aulopora, X J > £,. sur f ace > X 8 ; c, vertical section enclosing Aulopora, X 5 » 

 d, surface surrounding mouth of Aulopora, X 8. 



tubes are scattered among the apertures of the bryozoan, similar 

 to the " Caunopora " type of Stromatoporoids. Sometimes on 

 other corals. 



Surface with monticules of larger apertures at regular intervals; 

 apertures angular ; walls finely striated ; diaphragms remote in 

 older, more closely set in outer part of tube. 



Hamilton of Western New York and Michigan. 



