608 NEW YORK STATE MUSEUM 



but this is less primitive than in Schizocrania, its margins curv- 

 ing toward each other and approximating at the periphery. 

 These two genera are early (lower Siluric) and phylonepionic ex- 

 pressions of Orbiculoidea. In Schizobolus (middle Devonic) the 

 pedicle passage is a very short triangular notch, and the genus is 

 a late survival of the primitive stage represented by E u n o a . 



Trematobolus, Schizambon and Schizotreta are conditions in 

 which the pedicle has not only become inclosed but also in- 

 sheathed by a short tube. 



The generic characters of the genus Eunoa are thus well 

 defined, and no other shell carries so primitive an expression 

 of the orbiculoid type, a highly phosphatic shell, simple, wide, 

 triangular pedicle cleft and unmodified concentric surface 

 ornament. 



Horizon and locality. In graptolite shales of the age of 

 the Beekmantown limestone, on Deep kill near Melrose N. Y. 



Observations. The striking similarity of this organism to 

 that described by Jones and Woodward from the Moffat shales 

 of Dumfriesshire as Discinocaris gigantea leads to a 

 few remarks which are naturally suggested by this resemblance. 



Moffat series. The Moffat series of Dumfriesshire which has 

 been described in great detail by Lapworth 1 , is constituted of 

 black bituminous shale bands with interbedded grits, the former 

 carrying extensive graptolite faunules with such forms as 

 Monograptus, Dicranograptus, Olimacograptus, Dicellograptus, 

 Pleurograptus, Leptograptus, Thamnograptus and many other 

 genera which are present in the Deep kill section. Lapworth 

 has found evidence for regarding the comparatively slight thick- 

 ness of these beds as a sedimentary equivalent in the section 

 where they occur, of the Siluric series from the middle of the 

 Llandeilo up to the Wenlock, basing this deduction chiefly on the 

 range and limitations of the graptolite faunas. There is herein 

 a condition clearly parallel to that now determined for the 

 Hudson river beds of eastern New York, whose graptolites have 



1 See specially Lapworth. The Moffat series. Quar. jour. geol. soc. 

 1878. 34:240-346. 



