46 LOWER PENINSULA. 



over the opposite one ; by a great thickening of the walls, the crests 

 become obsolete. Pores are large and numerous. Diaphragms 

 developed in the thinner-walled tubes. Found in the Niagara 

 limestone of Point Detour, Drummond's Island, and in the expo- 

 sures of the Niagara group along the shore of Lake Michigan, in 

 the west part of the Upper Peninsula. 



Plate XVIII. — ¥\g. i represents fragments from Point of Barques 

 on Lake Michigan (southwest of the mouth of Manistic River). 



CLADOPORA, Hall. 



Ramose and anastomosing stems or laminar expansions, with 

 orifices on one or both sides, composed of thick-walled, elongate, 

 conical tubules, opening obliquely to the surface, with dilated 

 orifices. Tubules laterally connected by pores. Diaphragms have 

 originally been denied by the author in his genus Cladopora, but 

 their occasional development is proved by many actual observa- 

 tions, although usually the tube channels, in specimens, are found 

 open throughout all their length. 



The tube cavity of Cladopora is said to be destitute of longitu- 

 dinal furrows or crests, in distinction from Limaria and Striatopora, 

 but this is merely through habitual obsolescence of a character 

 which properly belongs to the entire Favositoid family, and which 

 in some of the most characteristic species of Cladopora has been 

 recognized in rudimentary development. 



CLADOPORA LAQUEATA, N. Sp. 



Large, reticulated, horizontal expansions, formed of round or com- 

 pressed elliptical stems, from two to four millimeters in diameter, 

 with narrow, intervening loops of elongate, lanceolate form. Tubes 

 very thick-walled. Orifices separated by broad interstitial spaces, 

 transversely oval, somewhat dilated, nearly one millimeter wide in 

 transverse direction, with a stout lip on the exterior margin ; the in- 

 terior margin impressed and confluent with the massive interstitial 

 surface. Pores plainly discernible. Diaphragms sometimes notice- 

 able, closing off the peripheral tube ends. By silicification the finer 

 surface details of the specimens are generally much impaired. 



