LOWER SILURIC SHALES OF THE MOHAWK VALLEY 19 



K4, which consists prevailingly of thin sandstone and arenaceous 

 shales of " Frankfort " aspect, still contains bands of black argilla- 

 ceous shale, which usually yield graptolites on examination. At the 

 base (120 feet from the top sandstone layer of the section) a band 

 (Mus. loc. 3767) has furnished: 



12 Climacograptus typicalis (c) 

 Lasiograptus eucharis (cc) 



The L a s i o g r.a ptus eucharis occurs in an unusually 

 large and broad mutation. 



Another graptolite horizon was found but 22 feet from the top 

 (Mus. loc. 3766). This contains: 



13 Diplograptus (Amplexograptus) macer nov. (c) 



The graptolite that characterizes this fauna is an extremely nar- 

 row and long form, hitherto not observed at other horizons and 

 therefore here distinguished by a new specific term (see Paleonto- 

 logic notes, p. 82). 



A survey of these localities as little suggests any sharp faunal 

 boundaries as do the lithologic characters of the rocks. The rock 

 is a black brownish weathering shale that strongly reacts with HC1. 

 This character does not change until K3 (with horizon n) is 

 reached, when the black shale becomes wholly argillaceous. Never- 

 theless there is distinct though gradual change in the faunal aspect 

 of the Utica shale as one passes upward. The basal beds at Mor- 

 phy's and Swartztown creeks were found to be characterized by 

 Corynoides calicularis and Diplograptus 

 mohawkensis, two fossils which are wholly foreign to 

 the Utica beds of the Utica section, or to the typical Utica beds. 

 Corynoides calicularis is in the Chuctenunda 

 section still abundantly found 220 feet above the base. Diplo- 

 graptus mohawkensis remains the most common fos- 

 sil, much longer, through 3 and 4, but in 5 it is replaced by 

 Lasiograptus eucharis which remains the dominant 

 graptolite to near the beginning of the transition beds, where it is 

 somewhat abruptly displaced by Climacograptus 

 spiniferus, (in 10) which hitherto had not been observed 

 in the section. Then also Climacograptus typicalis 

 appears and at the top a new species of Diplograptus. We may 

 add that Lasiograptus eucharis, Climaco- 

 graptus spiniferus and Cl im acograptus 

 typicalis continue into and through the " Frankfort " shale 

 in the lower Mohawk valley. 



