STATE GEOLOGIST. 85 



quence of the drift materials strewn over the surface, and the 

 perishable nature of the rock. Prom what has been said, it 

 appears that this group touches Lake Michigan, and that the 

 Huron and Hamilton Groups (if both exist) must pass entirely 

 beneath the lake, re-appearing probably in Mason, Oceana and 

 Manistee counties, while the Marshall Group prooeeds in the 

 direction of Newaygo and Lake counties. 



Details of stratification and fossils at the various outcrops 

 cannot, of course, be appropriately given at the present time, 

 nor even an enumeration of all the outcrops. 



The palaeontology of the Marshall Group possesses consid- 

 erable interest, both in consequence of the number of indi- 

 viduals and species found fossil, and the distinctness of the 

 fauna from that of other regions in the same geological horizon. 

 Considerable attention has been bestowed upon the collections 

 from this group, but not a single satisfactory identification 

 has yet been made. The most abundant and characteristic 

 fossils at the various localities belong to the genera Nucula, 

 (5 species,) Solen, (2 species,) Bellerophon, (3 species,) Ortho- 

 ceras (5 species), Myalina and Glymenia (5 species). Besides 

 these, I have referred to Gyrtoceras, 4 species, Cryptoceras, 

 2 species, Trocholites, 1 species, Goniatites, 5 species, Pleuroto- 

 maria, 1 species, Tellina, 1 species, Cardium, 2 species, Lucina, 

 1 species, Chonetes, Orthis and other Brachiopods, one or more 

 species each. 



There are, moreover, numerous species which have not yet 

 been particularly examined, among which are a few fish remains 

 and land plants. As I intend communicating to the public at 

 an early day, further particulars regarding this assemblage of 

 fossils, I refrain from extended remarks at the present time. 

 The delay experienced, however, in printing this report, ena- 

 bles me to append a few observations relative to the Clymeniae. 

 According to all authorities, the two genera Clymenia and 

 Goniatites are widely distinguished by the position of the 

 siphon, being interior in the former and exterior in the latter. 

 It is true that all my specimens of Cephalopoda from the Mar- 



