﻿32 II M. Seely — Genus Strephochetus. 



the fossil over a wide area, while as a constituent of bowlders 

 it has a still wider distribution. 



On the New York side of the lake, S. ocellatus has been found 

 at Plattsburgh and Chazj. In Vermont it has been observed 

 at Isle La Motte, while the finest displaj^s have been found in 

 the town of Ferrisburgh, at various points, particularly at Ball's 

 Bay just north and at Fields Bay just south of Fort Cassin. 

 At this latter locality surfaces of rock exposing several square 

 feet are crowded with this sponge to the exclusion of every 

 other fossil. Specimens have been gathered at points sixty 

 miles apart, and wherever the middle Chazy occurs, either on 

 the western or eastern side of Lake Champlain, there one may 

 look for S. ocellatus. More careful observations are necessary 

 to determine accurately the vertical range of the fossil ; prob- 

 ably, however, fifty feet would be a moderate estimate. 



2. Species. — To the type of the genus S. ocellatus there are 

 now to be added three species : S. Brainerdi, S. atratus, and 

 S. Richmondensis. 



S. Brainerdi, n. sp. 



A free calcareous sponge having the twining canals peculiar 

 to the genus, which structure may enlarge into furrows and 

 further into well-defined cylindrical canals, and these canals 

 may so increase in number and press upon each other that in 

 sections they appear polygonal. The" diameter of the large 

 canals varies from jij to ^J 7 of an inch. The size of this 

 species is greater than any other of the genus yet observed, 

 being frequently over an inch in length. Its outline is usually 

 oval in section, though in many cases the specimens are 

 irregular or angular as though they had been crushed by- 

 pressure. 



This form has as yet been observed only in some, of the 

 magnesian layers intercalated among the compact and fine- 

 grained layers of the Chazy rocks in the magnificent display 

 of these at the village of Chazy, N. Y. The specific name is 

 given in honor of Professor Ezra Brainerd, whose careful ob- 

 servations and accurate measurements have added much to 

 our knowledge of the series. 



S. atratus, n. sp. 



A free calcareous sponge, smallest of the genus yet recog- 

 nized, having the external appearance of S. ocellatus, with 

 the internal structure of S. Brainerdi, the small canals obscure, 

 the larger ones distinct. 



This form was obtained from the Black Eiver limestone at 

 McBride's Bay, S. Hero, Vt., and in the Black River lime- 

 stone at the quarry of west lime kiln, Chazy, N. Y. This little 



