On CalamoporcE in gravel deposits near Ann Arbor, Mich. 393 



Characteristic of this species, are obtusely polygonal concen- 

 tric rings of growth marking both faces of the diaphragms 

 and an obscure radial striation, which becomes more distinct on 

 the eroded surfaces. 



Usually three or four diaphragms are placed in a space equal 

 to the diameter of a tube, but sometimes only one, for the same 

 distance. The corallum is found in tabular fragments of several 

 inches thickness and nearly parallel tubes, or in biconvex cakes 

 With the lower side surrounded by an epitheca, which however 

 IS rarely well preserved. 



Calamopora Niagarensis Hall, and part of favosa Hall ; Calamopora 

 Guthlandica auctorum : Dania Huronka ? 



I adopt the name magaremis, in preference to Goi]ilandica, 

 because the first name is less abused, while the latter has been 

 applied to so many different species that nobodv knows which is 

 the genuine. Even Goldfuss himself confounded different corals 

 under that name. The Eifel specimens of Calamopora Gothlandica 

 are at all events totally different from the Niagara specimens. 



Under the name Niagarensis, I comprise forms which are found 

 associated, and do not differ from each other, except in the size 

 of their tubes, which varies from two to four millimeters in dif- 

 ferent specimens. The inside of the sharp-edged polygonal 

 tubes is covered with small delicate spinules; some specimens 

 appear to be entirely smooth, but, even in these, usually some 

 tubes can be found in which the spinules are preserved. 



Pores are small, not crowded, and with no elevated border, 

 from 1 to 4 rows may be counted on a side, the number of rows 

 on the circumference of a tube does not seem to exceed 15, more 

 ntly a smaller number occurs. Diaphragms flat, s 



slightly concave, or flexuous, in consequence of the development 

 of a few marginal depressions; or stellate, if these depressions 

 have become more numerous and more regular. Most frequently 

 from 5 to 12 such depressions are observed, but in some tubes I 

 have noticed more than 12. 



All these variations in the diaphragms can be observed at once 

 m a single specimen, but most frequently the diaphragms are 

 perfectly flat, horizontal, or occasionally oblique, their upper 

 face is also decorated with spinules, which however are seldom 

 preserved. 



I^istance of diaphragms variable from the thickness of paper to 

 ^i^ore than the diameter of a tube. This variation occurs some- 

 times in the prolongation of one and the same tube, or cluster 

 of tabes. 



A number of specimens, and those with closely approximated 

 diaphragms in particular, have a laminated structure, and the 

 Side pores are disguised by the densely crowded diaphragms, or 



