Handbook of Paleontology 287 



and trilobites, of which only traces have been observed 

 in the Normanskill, are frequently seen in the Snake Hill 

 shales. The formation has an enormous thickness, 3000 

 feet being considered a minimum measurement (Ruede- 

 mann). In the Hudson valley it forms the broad belt of 

 shales between the Normanskill shales and Wappinger 

 limestone at the bank of the river to the Skunnemunk 

 mountains and has a computed thickness in Orange 

 county of 1500 to 2000 feet which is regarded as a mini- 

 mum figure considering the width of the belt. The 

 fauna of these shales is a large one. It contains some 

 of the characteristic Canajoharie forms and also a fauna 

 that came in from the north. There are a number of 

 strange fossils that have not been found elsewhere. In- 

 cluded in the fauna are the graptolites Corynoides gracilis, 

 Diplograptus (Glyptograptus) amplexicaulis, Climaco- 

 graptus typicalis, Lasiograptus eucharis and Glossograp- 

 tus; the cystoid Edrioaster saratogensis; crinoids as Glyp- 

 tocrinus cf decadactylus (joints) and Heterocrinus gra- 

 cilis; bryozoans as Prasopora and Pachydictya; brachio- 

 pods as Dalmanella rogata (testudinaria) , Plectambon- 

 iies sericeus, Rafinesquina alternata and Zygospira re- 

 curvirostra; pelecypods as Cuneamya acutifrons, Cliony- 

 chia undata, Orthodesmaf subcarinatum; gastropods as 

 Lophospira bicincta, Tetranota bidorsata, Cyrtolites cf re- 

 trorsus; the conularid Conularia trentonensis ; cephalo- 

 pods as Spyroceras bilineatum and Endoceras protei- 

 forme; and trilobites as Eoharpes ottawaensis , Crypto- 

 lithus tessellatus, Triarthrns becki, Calymene senaria and 

 Isotelus gigas. 



The Schenectady beds (Ruedemann '12) receive their 

 name from typical exposures in the vicinity of Schenec- 

 tady. They overlie the Canajoharie shale and are now 

 known to be of upper Trenton age, though previously 



