84 LOWER PENINSULA. 



which locality the specimens represented on Plate XXXII. come. 

 The upper convex specimen on the left side of the plate is the 

 form corresponding with Milne-Edwards' Thecostegites. He has 

 described similar other forms under the names of Syringopora 

 Vernaiilli, Syr. Clcviana, and Mr. Billings describes a form under 

 the name of Syringopora Hisingcri, all of which arc distinguished 

 from one another by trifling modifications in their manner of 

 o-rowth. I consider them as mere varieties of one and the same 

 species for which I retain Billings' name. 



SYRINGOPORA HISINGERI. 



It differs from Syringopora tabulata by its more distant, some- 

 what flexuose tubules, with side connections in dispersed position, 

 and not in verticils. The tubules vary in size from half a milli- 

 meter to one millimeter. The three lower specimens in the upper 

 row of Plate XXXII. represent various fragments of this form, 

 found in the drift. Other specimens are found in which the tubules 

 are still further apart. The last-mentioned forms are all found asso- 

 ciated in the corniferous limestone of Michigan, Canada, Ohio, New 

 York, Indiana, Kentucky, etc. 



SYRINGOPORA NOBILIS, Billings. 



Colonies of large tubes, from five to eight millimeters in diameter. 

 In some the tubes are quite remote from each other, and connected 

 by distant, transverse branch channels ; others have the tubes 

 more closely clustered and of smaller size. I am not positive of the 

 specific identity of these forms, but provisionally arranged them 

 under Billings' name, intended for the form with large, remote stems. 

 Found in the corniferous limestone, and in the Hamilton group of 

 Michigan and Canada ; similar forms occur in the Hamilton group 

 of Iowa. 



On Plate XXXII., lower row, right-side figure, is represented a 

 specimen found in the drift of Ann Arbor, associated with cornifer- 

 ous limestone fossils ; the adjoining central specimen is a young 



