128 



Report of the State Geologist. 



For the absence in the latter of the nepionic expansion of the conch so 

 notable in onr species of Bactrites, we can offer no further explanation than 

 that afforded by a comparison with the goniatites here studied. This expan- 

 sion is seen in Tornoceras, Manticoceras, Probeloceras, etc., but not in the 

 same degree in each genus, nor, again, to like degree in members of the same 

 genus. Thus it is much the more conspicuous in Torn, bicostatum than in the 

 earlier Tom. imiangularej it is clearly, though not conspicuously, developed 

 in Mantic. JPattersoni, but we have given a figure of Mantic. mtwmescens in 

 which it is very prominent. 



We should have no justification in concluding from the foregoing observa- 

 tions that the Wissenbach specimen is not a Bactrites, on the contrary the 

 very differences which have been pointed out as existing between this early 

 shell and the typical Bactrites, B. gracilior, are in themselves evidences of 

 time and ontic changes within the same genus. 



Localities. Bactrites gracilior occurs in the Styliola limestone on Canan- 

 daigua lake and at Middlesex. In the normal fauna it is widely distributed 

 through the shales and calcareous nodules, but becomes less common in the 

 arenaceous beds. It has been found at various localities in Yates, Ontario and 

 Livingston counties, in the Genesee valley and in Wyoming county, and also 

 in Erie and Chautauqua counties. kSpecimens which can be referred to this 

 species with certainty are more numerous in the eastern counties than in those 

 bordering on lake Erie, where their place seems to be largely taken by the 

 other species, B. aviculuin. 



Bactrites aciculum, Hall (sp.). 



Plate IX, Figs. 17-22. 



1843 Orthoceras aciculum, Hall. Geology of New York; Report on the 



Fourth District, p. 243, fig. 4. 

 1879 Goleolus aciculum, Hall. Palaeontology of New York, vol. v, pt. 2, 



p. 1 ST, pi. xxxii A, figs. 11-15. 



To this species, whose representatives, as above cited, are flattened speci- 

 mens from the shales of the Genesee and Portage beds, I refer a shell dis- 

 tinguished from Bactrites gracilior in its decidedly more elliptical conch 

 section ii! all stages of growth and probably also in its smaller protoconch 

 and more slender nepionic shell. It is of so much less frequent occurrence 

 than B. gracilior that it is not easy to indicate from our material other specific 

 characters than those mentioned. 



