114 DEVONIAN FAUNA. 



2. PoTERiocERAS Marei, WMdbome. PI. VII, figs. 4, 4 a, 4 &. 



1889. GoMPHOCEEAS Maeei, Whidh. Geol. Mag., dec. 3, vol. vi, p. 29. 



Description. — Shell almost straight, ovate above, tapering below, rather small. 

 Ventral outline convex, becoming straight below. Dorsal outline concave near the 

 aperture, then convex on the lower part of the body- whorl, and then straight on 

 the septal part. Lateral outlines convex above, straight below. Septa straight, 

 rather narrow, being distant from each other about one-eighth their height above ; 

 the proportion diminishing towards the apex, as their height remains constant, 

 while their width decreases. Section elliptic, the ventro-dorsal being to the 

 transverse diameter in the ratio of 5 : 6. Surface (of the cast or inner shell) 

 marked with numerous fine, distant, indistinct, longitudinal, rounded lines, which 

 vanish on the upper part of the body-whorl. Siphuncle doubtful. 



Size. — Length, 46 mm. (apical end defective) ; greatest dorso-ventral diameter, 

 25 mm. ; lateral diameter about 28 mm. 



Locality. — Wolborough. A single specimen is in Mr. Vicary's Collection. 



Bemarks. — This seems a well-marked form, and is fairly definite, although the 

 single specimen is rather crushed, and is injured at both extremities. The 

 general contour, the longitudinal striae, and the obliquity of the aperture distinguish 

 it from the surrounding species. 



Affinities. — Goniphoceras amygdala, Barrande,^ has the body-chamber less swollen 

 and the dorsal side straighter. It is similar in its section. 



Cyrtoceras speciosum, Barrande,^ and G. aduncum, Barrande,^ have less convex 

 lateral outlines, and much narrower chambers. 



Orthoceras subarcuatum, Portlock,* which that author somewhat whimsically 

 places between the genera Orthoceras, Cyrtoceras, Phragmoceras, and GoinpJioceras, 

 is more elongate than the present form. 



Gomphoceras inflatum (Groldfuss) is, judging, from F. Romer's figure,^ more 

 elongate, ovoid, and with broader chambers. 



Cyrtoceras imperans, Barrande," is a very much larger species, being more than 

 a foot in length. It evidently belongs to the same genus, and is closely allied, 



1 1865, Barrande, ' Syst. Sil. Boh^m.,' vol. ii, p. 273, pi. Ixxvii, figs. 23—26, and pi. Ixxx, figs. 1—17, 

 Et. E. 



2 1866, Ibid., p. 692, pi. clxx, figs. 1—7 ; pi. clxxviii, figs. 1—7, and pi. ccxvii, fig. 5, Et. E. 



3 Ibid., p. 683, pi. clxix, figs. 9—14, and pi. clxxxi, figs. 10, 11, Et. F. 

 * 1843, Portlock, ' Eep. Geol. Londonderry,' p. 374, pi. xxviii, fig. 9. 



5 1876, Eerd. E5mer, ' Leth. Pal.,' pi. xxx, fig. 6. 



'' 1877, Barrande, ' Syst. Sil. Boheme,' vol. ii, Suppt., p. 25, pi. cccclxii, fig. 1 ; pi. cecclxiii, 

 figs. 4, 5 ; pi. cccclxxxv, figs. 1, 2, Et. G. 



