measures 27 × 36.8 mm and a smaller cotype in the same collection, 24.5 × 32.4 mm. The proportions of the carapace hence lie between 2 : 3 and 3 : 4.
The tergite of the type is but 1.8 mm long. A nearly entire specimen from Onondaga Valley possesses a carapace 20.6 mm long; its preabdomen (perhaps somewhat pushed together) measures 26.5 mm and the remaining five postabdominal segments about 30 mm. It is widest at the second sternite (30.5 mm). The abdomen figured by Whitfield is complete to the telson, which is lacking. The specimen is probably slightly reduced in the figure, judging from the size of the accompanying carapace, and we have not the original at hand. The preabdomen in the figure is 31.5 mm long and about 33.8 mm wide. The postabdomen is 35.8 mm long and shrinks from a width of about 24 mm to 10 mm in the last segment.
Horizon and localities. The type came from a loose boulder near Cazenovia, Madison co., N. Y., which by its lithologic character and the associated fragments of Spirifer vanuxemi shows its derivation from the Manlius beds. Besides this rather poorly preserved specimen the State Museum possesses a series of carapaces and a nearly complete specimen of this extremely rare form. This entire specimen was found loose in Onondaga Valley by Prof. Philip F. Schneider and appears also to have come from the Manlius limestone. Of the carapaces, one was collected by the authors in the town of Litchfield in Manlius limestone, not less than 100 feet above the Eurypterus horizon in the Bertie waterlime; another was found loose on Jerusalem hill (probably also from Manlius limestone, according to the lithologic aspect of the slab); still another was obtained at Cherry Valley falls. A series of carapaces, some of relatively large size, were obtained in the layers of the Manlius formation at the Kolb farm, Crane's Corners, near Jerusalem hill, Herkimer co., and some segments in the waterlime of the Manlius at Manlius village. From this it appears that there is a continuous waterlime bed near the top of the Manlius formation, extending from Onondaga county to Albany county and the species seems to be confined to this layer. Professor Whitfield's
