from the Taconic Series at Canaan, N. Y. 253 



the conclusion that it is most probably a species of Fenestella 

 or some closely related generic form ; but its specific determin- 

 ation has not been found possible. The specimen is principally 

 interesting as showing that very delicate organic structures 

 have been preserved in a limestone which is, for the most part, 

 so highly metamorphic, that nearly every vestige of fossils has 

 been obliterated ; and further, as an indication that, at some 

 favored locality in this limestone, a large and well-preserved 

 suite of decisive specimens will yet be obtained. 



Brachiopoda. — Fig. 9 appears to us to represent, most prob- 

 ably, the cross section of a brachiopod of about the size and 

 form of the well-known Trenton species Orthis occidentalis. It 

 was discovered by polishing a surface of the dark Canaan 

 limestone, and is associated with other organisms. Similar, 

 though less convincing sections, on which we have put the 

 same interpretation, have been observed in other slices which 

 we have studied, and are probably of the same nature. Apart 

 from these examples, however, no forms certainly referable to 

 the Brachiopoda have been obtained from the Canaan lime- 

 stones, unless some of the structures exhibited in figs. 3 f, i, 

 represent sections of the ribs of small Orthidce, or allied forms, 

 which may possibly be the case. 



Gasteropoda. — The fossils of this class furnished by the 

 Canaan limestones, afford the most decisive testimony concern- 

 ing the age of the rocks in question of any that we have exam- 

 ined. They occur in considerable numbers in certain portions 

 of this limestone, associated with comminuted crinoidal remains 

 and other organisms, and are well shown both in transparent 

 rock-sections and upon carefully polished surfaces of ordinary 

 hand-specimens (see fig. 1). We refer the majority of the 

 forms met with to two species, one of which (figs. 10 a—i) appears 

 to be, with but little doubt, the Pleurotomaria subtilistriata of 

 Hall (Pal. N. Y., vol. i, p. 172, pi. 37, figs. 5 a-d)- and the 

 other (figs. 11 a-f), with even less doubt, the well-known Tren- 

 ton species Murchisonia gracilis (Pal. N. Y., vol. i, p. 181, pi. 

 39, figs. 4 a-c ; ibid, p. 303, pi. 83, figs. 1 a-c). Professor Hall 

 states, in his description of P. subtilistriata, that the majority of 

 the specimens are so small as to be scarcely visible to the naked 

 eye; and we have found this true of the Caanan species. This 

 species appears abundantly in sections of the Eochdale Tren- 

 ton, and slices from the two localities, placed side by side, 

 apart from the apparent absence in the Canaan rock of the 

 common Rochdale coral /Solenopora (Chceteles) compacta, are 

 practically undistinguishable. 



Associated with the above species there occur the forms 

 shown in figs. 12, 13, 14 and 15. which we look upon as prob- 

 ably representing other species of Gasteropoda, but are unable 



