276 



Report of the State Geologist. 



western form, and on well preserved specimens they are to be found on the 

 hinge area. The delthyrium is narrow and the area on each side distinctly 

 grooved as in 8. angustus. In a number of specimens the beak is slightly 

 incurved, and the area consequently somewhat concave. This may be partly 

 due to compression, but in some cases it is normal. A typical pedicle- valve 

 measures 26 mm. along the hinge line. The height of the cardinal area is 12 

 mm. and the height of the valve 13 mm. 



114. Spirifer fimbriatus, Conrad. 



1867, Hall, Pal. N. Y., vol. 4, p. 214, pi. 33. 



This species occurs as low as the Pleurodictyum beds, but it is very rare. 

 "With a few exceptions from the shales of this level, I have found it only in 

 the S demissa and Stictopora beds and in the upper Encrinal limestone. It 

 is very abundant in the former bed but the test is seldom well preserved. 



115 Spirifer subumbonus, Hall. 



1867, Hall, PaL K Y., vol. 4, p. 234, pi. 32. 



This species is rare at Eighteen-mile creek. A single specimen showing 

 the characteristic surface markings was found at Section C, one and one-half 

 to three feet below the Encrinal limestone. In the upper Moscow shales, 

 down to four feet from the top, but principally between one and one-half and 

 two and one-half feet from the top, occur a number of specimens of the 

 species, none, however, showing the pits resulting from partial exfoliation. 



Genus Amboccelia, Hall. 



116. Amboccelia umboxata, Conrad. 



1867. Hall, Pal. N. Y., vol. 4, p. 259, pi. 44. 



This is one of the most abundant fossils in the shales of the Hamilton 

 group at Eighteen-mile creek. It occurs in the Lower shales, in the Encrinal 

 limestone, and in the Moscow shales. In the latter it constitutes layers 

 several inches thick where almost no other fossil is found. It is rare in the 

 Encrinal limestone, but common in the Lower shales, and m the transition 

 shales down to twenty-two feet below the Strophalosia bed. It has also been 

 noticed in the Marcellus shales. 



1 16(a) Amboccelia umboxata var. nana. n. var. 

 Shell small. Pedicle-valve ventricose, broader than the typical forms of 

 the species. Height proportionally less than that of ordinary forms. Sinus 



