102 DEVONIAN FAUNA. 



C. semulnm, Hall,'^ is also straighter, and the fimbrige seem more regular. 



Gyroeeras cyclops, Hall/ seems most nearly to approacli it of the American forms 

 in general facies and in the character of the lamellae, and its curvature is probably 

 the same ; but its minor transverse ornamentation is coarser and more distant. 

 It also has more defined, broader, and much more numerous longitudinal bands 

 than those in C. Leei. 



2. Genus. — Cyrtoceras, Goldfuss. 



This is one of the largest genera of the Cephalopods. It contains forms with 

 simple orifices, which are slightly and in general regularly arched, but not so much 

 so as to form a spire. Its siphuncle is generally situated near the ventral margin, 

 but occasionally is central or sub-central. It has been divided into genera and 

 even families by Hyatt and others, but Barrande has reunited the various forms 

 in the one great genus. It extends from the Lower Silurian to the Permian. 



From the localities at present under review the number of forms that have 

 come to my notice are comparatively few. They chiefly belong to the section of 

 the genus which was separated by Hyatt under the name of Zitteloceras,^ a genus, 

 however, which is not upheld by Mr. Foord. Of this section G. lamellostim, Hall* 

 (not d'Archiac and de Verneuil) is the earliest representative, occurring in the 

 Trenton Limestone; and G. quindecimale, Phillips, G. fimhriatum, Phillips, 

 G. lamellosum, d'Archiac and de Verneuil,^ and G. Jason, Hall,® are Devonian 

 species belonging to the same type. 



The other species of Gyrtoceras belong to the section Brevicones, and are 

 here represented, with one exception, by only a few poor and indistinct specimens. 



1. Cyrtoueras quindecimale, Phillips. PI. X, figs. 1, 1 a, 2, 2 a. 



1841. Ctbtoceeas quindecimale, PM. Pal. Foss., p. 114, pi. xliv, fig. 216. 



1842. Ctbtoceeatites quindecimalis, D'Arch. and de Vern. Geol. Trans.,8er. 2, 



vol. vi, pt. 2, p. 386. 



1 1879, Hall, ' Pal. N. Y.,' vol. v, p. 371, pi. xcvii, figs. 1—9 ; and pi. xcviii, figs. 4, 8. 



2 Ibid., p. 387, pi. ci, fig. 1 ; pi. cii, fig. 1 ; pi. ciii, figs. 1, 2 ; pi. civ, figs. 1, 2. 



3 1883, Hyatt, ' Proceedings Bost. Soc. Nat. Hist.,' vol. xxii, p. 84. 



-i Hall, 1847, ' Pal. N. Y.,' vol. i, p. 193, pi. xli, fig. 2. As d'Archiac's name has the priority I should 

 like to suggest the name of C. Foordii for Hall's species, which was pointed out to me by Mr. Foord. 



5 1842, D'Arch. and de Vern., ' Geol. Trans.,' ser. 2, vol. vi, pt. 2, p. 348, pi. xxviii, figs. 4, 4 a, b. 



6 1879, Hall, 'Pal. N. Y.,' vol. v, pt. 1, p. 381, pi. 1, figs. 1, 2. 



