A NEW GENUS OF PALEOZOIC BRACHIOPODS, EUNOA 



WITH SOME 

 CONSIDERATIONS THEREFROM ON THE ORGANIC BODIES KNOWN AS 



DISCINOCARIS, SPATHIOCARIS AND CARDIOCARIS 



BY JOHN M. CLARKE 



Plates 5-8 

 While exploiting a section of the " Hudson river shales " near 

 the village of Melrose, Rensselaer co. N. Y., in the season of 

 1901, Dr. R. Ruedemann uncovered a remarkable succession of 

 graptolite faunas representing the associations of those organ- 

 isms found and heretofore described by Hall and others from 

 the shales of the Quebec formation at Point Levis and Ste 

 Anne in Canada. Of this interesting occurrence adding in a 

 very important measure to our knowledge of the ancient faunas 

 of New York, Dr Ruedemann has already given a preliminary 

 account in this report, with a summary of the variation 

 and vertical distribution of the graptolites. These grapto- 

 lite-bearing horizons, three in number in the section exposed, are 

 black shales interbedded with green grits and gray sands, and, 

 while they have produced graptolites in great profusion and 

 variety, other organisms prove to be very infrequent; some 

 small oboloids like Paterula, two specimens of a great Lingula, 

 the largest known from the Paleozoic, which approaches in 

 general features L. quebecensis Billings from the Point 

 Levis section, and several examples of a very large shell in 

 which we recognize an interesting new type of brachiopod struc- 

 ture and purpose to describe under the generic name 



EUNOA 



Inarticulate, subcircular, disk-shaped shells of discinoid ex- 

 pression. Brachial valve slightly convex with apex situated 

 between the center and posterior margin of the valve; pedicle 

 valve flat with wide open triangular foramen having its apex at 

 the center of the disk and with margins rapidly diverging to 

 the periphery. Shell thin, chitinous, phosphatic; surface with 

 raised concentric filiform lines and finer radial intralaminar 

 striae. 



