52 



LOWER PENINSULA. 



the orifices, but in others of equally well-preserved specimens no 

 crests are recognizable. Lateral pores well developed. Transverse 

 diaphragms have not been observed. The casts of tubes often 

 found in drift specimens are always uninterrupted, thread-like, lat- 

 erally connected by short transverse bars representing the pores, and 

 exhibiting the intercalation of new young tubules, connecting by a 

 perforation at the apex with their mother-tubes. 



Found abundantly in the drift of Michigan, in a porous cherty 

 rock containing many other corniferous limestone fossils. In Canada 

 and New York it is common in the corniferous limestone ; occurs 

 also at the Falls of the Ohio. 



Plate XXI. — Fig. 2 represents a number of branchlets of variable 

 form. The two lower figures on the left side are excepted ; they 

 are described under the name of Cladopora rimosa ; but in the lower 

 tier of this plate the smaller central specimen is considered as a 

 variety of Cladopoi'a labiosa. 



CLADOPORA RIMOSA, N. Sp. 



Reticulated expansions of small teretiform or elliptically com- 

 pressed stems, much resembling the former species. Orifice openings 

 very oblique to the surface, transversely compressed, fissure-like, 

 margined by a sharp closely-appressed lip on the outer side. Di- 

 ameter of orifices in transverse direction from one half to two thirds 

 of a millimeter ; interior tube channels cylindrical and much nar- 

 rower. Interstitial spaces large and flat. This form is the usual 

 associate of Cladopora labiosa, and may perhaps be only a variety 

 of that species ; but the two forms are so constant, not merging into 

 one another through transition forms, that I believe them to be dis- 

 tinct. Found in the drift of the Lower Peninsula. 



Plate XXI. — Fig. 2, the two lower left-hand stems. The 

 larger forked specimen is broken off from a disciform basal expan- 

 sion incrusting the stem of a Cyathophyllum Hallii. 



CLADOPORA PINGUIS, N. Sp. 



Horizontally expanded, branching and anastomosing stems of 

 usually compressed elliptical form, but sometimes cylindrical. Di- 

 ameter of stems from five to ten millimeters. Orifices in the older 



