FOSSILS OF THE DEVONIAN. 



203 



Group. The latter is more slender, and has a less gibbous chamber of habi- 

 tation. 



Formation and locality. Upper horizon of the Devonian limestone; The 

 Gate, northwest of Eureka, Eureka District, Nevada. 



Genus CYRTOCERAS Goldfuss. 



Cyrtoceras Nevadense, n. sp. 



Plate xvii, figs. 7, 7 a. 



This species is represented by a portion of the chambered tube SO" 1111 

 in length ; the apical extremity, beyond a diameter of 1 O mm , and the cham- 

 ber of habitation having been broken away. 



Shell small, regularly curved, the depth of the arc of curvature being 

 2 mm in a length of 30 mm . Transverse section subcircular. Apical angle of 

 the lateral faces about 10. Air-chambers numerous, varying in depth from 

 2 mm to 3 mm in a distance of 30 mm , the larger extremity having a depth of 

 1 7 mm and the apical section of 1 O mm . Septa smooth, with a concavity a little 

 less than the depth of the air-chambers. Sutures horizontal, with a slight 

 backward curvature on the dorsal side. Siphuncle central. Test thin. 



Surface marked by lines of growth that have a somewhat obtuse sinus 

 on the ventral side. The internal mold preserves a trace of the exterior 

 markings of the test. 



This species resembles Cyrtoceras ( Gomphoceras) metula Hall (Pal. N. Y., 

 vol. v, pt. 2, p. 360), of the Upper Helderberg Group of New York. It 

 differs in the central position of the siphuncle, apical angle, and curvature 

 of the sutures. 



Formation and locality. Lower horizon of the Devonian limestone, 

 Comb's Peak, Eureka District, Nevada. 



Genus GONIATITES De Haan. 



Goniatites desideratus, n. sp. 

 Plate xvii, fig. 10. 



Shell discoid; estimating from the depth of the umbilicus, the thick- 

 ness of the disk is about 10 mm . There were probably four volutions; two 



