lO LOWER PENINSULA. 



created through mistaking compact, short-jointed specimens of 

 Syringopora tabulata for the type for a new genus, which assertion 

 I shall prove farther on by giving a detailed description of the 

 species. I have, in view of the above statements, reduced the six 

 sub-orders of Favositidai to three, namely, FaiwsitincE, Halysitince, 

 and CohinuiaricB, under which headings I will describe the genera 

 and species found in the State of Michigan, taking the liberty 

 sometimes of drawing into the descriptions, specimens found in 

 the foreign territory of the neighboring States, when I find it 

 necessary for a full illustration of a certain group of organisms, 

 of which the material found in the State is too imperfect. In the 

 production of photographic figures specially, I had frequently 

 to resort to specimens not found in Michigan localities — not that I 

 am without indigenous ones of the same order, but because these 

 are in a less perfect condition. 



MILLEPORID^. 



HELIOLITES, Guettard. 



Large visceral tubes, circular, scarcely or not at all projecting 

 above the general surface, radiated by twelve longitudinal crests, 

 not reaching the centre,' and often being only low, spinulose carinae. 

 Numerous transverse diaphragms intersect their channels, Coe- 

 nenchym abundant, formed of much smaller, not radiated, poly- 

 gonal tubules, which, divided by regularly disposed, transverse 

 diaphragms, represent vertical rows of subquadratic cell spaces 

 filling the interstitial space between the larger circular tubes. No 

 lateral anastomosis between tubes or cell spaces. 



Several species of Heliolites occur in the Niagara group of Michi- 

 o-an. The specimens are all found in silicified condition, and the 

 more delicate surface characters have suffered partial obliteration 

 by the process of petrification. 



