SUMMAR1 OF RESULTS. 



the great Corniferous coral reef of the east, occur at the upper horizon, and 

 Syringopora perelegans, of the same formation in New York, ranges through- 

 out the group in Nevada. The occurrence of rare species and those of 

 limited range in the eastern Devonian is not an unusual feature, as we 

 find Lingula Lcena, Strophodonta Patersoni, Chonetes hemispkerica, Productus 

 truncatus, etc. The Trilobita also show the great range of the two species 

 heretofore regarded as restricted to certain localities, viz, Proetus Halde- 

 mani and P. marginalia, and also the more widely distributed Phacops rana. 

 Among species of a greater range there is the well-known Pterinea flabdla 

 in association with other forms of the Upper Helderberg formation at the 

 Lower Devonian horizon; and Sanguinolites rigidus and 8. ventricosus, of the 

 Chemung Group, occur in the upper beds of limestone. The Gasteropoda 

 are shown by Platyostoma lineatum, so abundant in the Hamilton formation 

 of New York, and eight species of Platyceras, five of which are identical 

 with eastern species, as are the four species of Tentaculites and the minute 

 Styliola fissurella representing the Pteropoda. 



The fortunate discovery of the interior of a dorsal valve of a rather 

 large species of Lingula, L. Whitei, affords the means of comparison of the 

 same parts of the shell with a Silurian and recent species of this genus, and 

 proves the great structural similarity of the three species so widely sepa- 

 rated in geologic time (Plate xxi, figs. 18, 19, 20). 



The fauna of the White Pine shale in the White Pine District is in 

 many respects a peculiar one, combining as it does species ranging from the 

 Middle Devonian into the Lower Carboniferous. The stratigraphic position 

 of the shale is at the summit of the Devonian system and at the base of 

 the Carboniferous; it is overlain in the Eureka District, where the section is 

 unbroken, by a massive belt of conglomerate before the limestones carrying 

 the Lower Carboniferous fauna appear in the section. The strongly- 

 marked Carboniferous species are, Spiriferina cristata, Retzia radialis, Athyris 

 suUamellosa, and Cardiomorpha Missouriensis ; these are associated, at the 

 same horizon, with such Devonian species as Distinct, Lodensis, Productus 

 subaculeatus, Ambocoelia umbonata, RTiynchonella(L.} quadricostata, Aviculopecten 

 catactus, and Lunulicardium fragosum. 



Messrs. Hall and Whitfield (Geol. Expl. Fortieth Par., vol. iv, p. 201) 



