LOWER SILURIC SHALES OF THE MOHAWK VALLEY 121 



the genus Ulrichia with some doubt. It is usually as at Canajoharie 

 associated with Primitiella unicornis in the lower Tren- 

 ton and in the " Utica " of Cincinnati. 



Eurychilina subradiata Ulrich 



PL 9, fig. i6 



A specimen of this species which has been recorded by Doctor 

 Ulrich (Jour. Cin. Soc. Nat. Hist., 1890, 13:126; Geology of 

 Minnesota, part 2, 1897, 3:661) from " Birdseye and Lower 

 Trenton" of the Middle West (Minnesota-Tennessee) was also 

 collected in the shaly basal Trenton of the Canajoharie section. The 

 New York type is according to Doctor Ulrich a close derivative of 

 the western form which is there a good Black River species. 



Primitiella unicornis Ulrich var. 

 PI. 9, fig. 13, 14 



This minute ostracod was first made known by Doctor Ulrich in 

 1879 (title 8, page 10, plate 7, figure 4), and later more fully 

 described and illustrated in the Geology of Minnesota (title 38, 

 page 649). It is stated by its author to occur abundantly in the 

 lower part of the Cincinnati group about Cincinnati and also recorded 

 by the same authority from near the base of the "Hudson River 

 group " in Minnesota and in a slightly different variety from Mani- 

 toba (title 15, page 50). Professor Nickles (title 49, page 71) 

 records it from his lowest division of the " Utica " at Cincinnati. 

 Doctor Ulrich has denoted the Canajoharie form as corresponding 

 to the " basal Trenton variety." This variety appears to us to be 

 distinct from the type of the species in being more elongate and 

 thicker in the posterior part. The spine is somewhat larger and 

 the slight node in the dorsal depression larger. 



It has been observed by us in this State only in the lower part 

 of the Canajoharie shale. 



Ceratopsis chambersi (Miller) var. 



PI. % fig. 15 



The Indian Ladder beds at the Indian Ladder have furnished us 

 an ostracod which like many of its associated forms has before been 

 only known from the Cincinnati region, whence it was first described 



