58 LOWER PENINSULA. 



lives of the genus, and positively differing from Striatopora flexuosa, 

 Hall, found in the same geological horizon, I thought it proper to 

 describe even a fragment when well characterized. 



Orifices obliquely funnel-shaped, joining with edged margins. 

 The body side of the orificial walls is spreading and forms part of 

 the exterior walls of the orifices above ; the outer side of the 

 oblique orificial funnels is margined by an erect semicircular lip. 

 Diameter of orifices in transverse direction two millimeters ; in 

 longitudinal three millimeters. Twelve deep longitudinal furrows, 

 with intermediate obtuse crests, give the cells a star form. The 

 tubes are distinctly intersected by diaphragms with marginal de- 

 pressions. Pores are somewhat obscured by the rough silicified sur- 

 face of the specimen, but are recognizable. Found in the Niagara 

 group of Point Detour, Lake Huron. 



Plate XXIV. — Fig.*!^ upper fragment, natural size. Striatopora 

 flexuosa, Hall, has not been observed among the fossils of the Ni- 

 agara group in Michigan. 



STRIATOPORA RUGOSA, Hall. 

 Synon., CvATHOPHORA lowENSiS, Owen. 



Stems with dichotomous branches, from five to ten millimeters in 

 diameter, composed of very thick-walled tubes opening obliquely 

 to the surface, with dilated mouths, bounded on the exterior side 

 by a prominent semicircular lip. The inner body side of the walls 

 of the orifices is flattened, spreading into a common, broad, interstitial 

 mass. Diameter of orifices two millimeters ; of interior channels one 

 millimeter. Pores large, distant. Diaphragms not observed. The 

 radial striai are, in all the numerous specimens which I have exam- 

 ined, totally obsolete, for which reason this form would have a more 

 appropriate place under the genus Cladopora. 



Occurs frequently in the Hamilton strata of Thunder Bay, and 

 is found in the drift. L^J^/ 



Plate XXIV., Fig. -2*-^ — The s unt ml figure represents a stem from 

 Thunder Bay. 



