302 HALL AND SARDESON — PALEOZOIC FORMATIONS OF MINNESOTA. 



The fossils are : 



Analoteichia impolita, Ulrich. 

 Pachydictya foliata, Ulrich. 

 Stictoporella frondifera, Ulrich. 

 Leptsena sericea, Sowerby. 

 Lingula elderi, Whitfield. 

 Orthis perveta, Conrad. 

 0. tricenaria, Conrad. 

 Rhynchonella ainsliei, X. H. Win- 

 chell. 



R. minnesotensis, Sardeson. 

 Streptorhynchus filitextum, Hall. 

 Zygospira recurvirostris, Hall. 

 Helicotoma planulata, Salter. 

 Murchisonia gracilis, Hall. 

 Pleurotomaria subconica, Hall. 

 Raphistoma lenticulare, Emmons. 

 Productella Minneapolis, Sardeson. 



The Stictopora (or upper Blue) Bed. — This layer has a thickness of 

 about 30 feet. It is made up of a dark-green rock, massive rather than 

 shaly in its structure, and quite argillaceous in its composition. It car- 



Piguee 7. — Lenticular Segregations of Fossils in the Stictopora Bed, Saint Paul. 



Lenses consist of closely packed and thoroughly cemented fossils within the muss of calcareous 



shale. 



ries a few crystalline slabs composed of firmly cemented fossils (figure 

 7). This bed weathers so rapidly as to give it the appearance of being 

 very fossiliferous, but it is probably less so than the beds above. It 

 affords a good illustration of effectual weathering when exerted on rock 

 made up of such diverse elements. 

 The fossils are : 



Raufi lla filosa, Ulrich. 

 R. palmipes, Ulrich. 

 Pachydictya jimbriata, Ulrich. 

 Phylloporina reticulata, Hall. 

 Prasopora contigua, Ulrich. 

 Stictopora mutabilis) Ulrich. 

 Stictoporella cribrosa, Ulrich. 

 ('nut in halli, Sardeson. 

 C. setigera, Hall. 

 C. trentonensis, Hall. 



Zygospira recurvirostris, Hall. 

 Bellerophon hiloLittnx, Sowerby. 

 Bucania bidorsata, Hall. 

 Cortchopeltis bbtusa, Sardeson. 

 Cyclonema semicarinatum, Salter. 

 Holopea symmetrica, Hall. 

 Murchisonia gracilis, Hall. 

 M. milleri, Hall. 

 M. tricarinata, Hall. 

 Pleurotomaria clivosa, Sardeson. 



