CARBONIFEROUS FOSSILS OF IRELAND. 15 



GONIATITES OBTUSUS. Phil. 

 Goniatites obtusus. Phil. Geol. York. 



Sp. CIi. — Discoid, gibbous, somewhat compressed, ■with nearly parallel sides, and broad, obtusely -rounded 

 back ; umbilicus very small ; surface, when well preserved, very finely striated transversely ; stria3 waved ; 

 septa, dorsal lobe small, obscurely bifid, dorsal sinus angular, acute ; first lateral lobe three times the lent^th of 

 the dorsal, oblong, rounded ; lateral sinus wide, mucronatc. 



This species bears some resemblance to the Goniatites striatus and G. crenistria in general appearance, 

 but is distinguished from the first by its transverse striae, smaller umbilicus, and by its rounded lateral lobes, 

 and from the latter by the surface not being reticulated ; the back is broad and rounded, but the sides are but 

 slightly convex ; diameter one inch six lines, thickness ten lines. 



Goniatites reticulatus. Phil. 



Goniatites reticulatus. Phil. Geol. York. 



Sp. CIi. — Discoid, depressed, back angulated; umbilicus conical, smooth, with an angular margin; surface 

 with acute transverse branching, curved striaa, crenulated by fine spiral lines ; septa, dorsal lobe short, obscurely 

 bifid, dorsal sinus small, rounded ; fii-st lateral lobe narrow, rounded ; lateral sinus large, mucronate. 



It sometimes happens that casts only of the smooth conical umbilicus remain, but more frequently it 

 occurs crushed or flattened, with the surface perfect, shewing distinctly tlie beautifully curved dichotomous strise, 

 wliich, under the lens, are seen to be crossed by delicate spiral strise. The young shells are more globose, and 

 have a rounded umbilicus. Diameter from one to two inches. 



Goniatites sph^ricus. Mart. sp. 



Goniatites sphsericus. Mart. Pet. Derb. — Ammonites sphaericus. Soic. Min. Con. — Goniatites sphaericus. Phil. Geol. York. 



Sp. Ch. — Globular, umbilicus small, acute-edged; surface spirally striated; septa, dorsal lobe bifid, dorsal 

 sinus short, acute, first lateral lobe obtuse, four times the length of the dorsal lobe ; second lateral lobe very 

 obtuse, nearly as long as the first. 



This species is almost perfectly spherical in general form ; the umbilicus is small, rounded, and with a sharp 

 edge ; when finely preserved the surface is spirally striated, but it is more commonly found without the exter- 

 nal shell. Diameter one inch ten lines, thickness one inch five lines. 



Goniatites sph.eroidalis. M'Cojf. (PL IV. fig. 18). 



Sp. Ch. — Spheroidal, sides slightly flattened, thickness equal to two-thirds the diameter; umbilicus rathe 

 large, acute-edged ; shell marked with very fine transverse strise, and having faint, internal, sigmoidal ridges ; 

 septa, dorsal lobe bifid ; lateral lobe very short, scarcely exceeding the dorsal lobe in length, broad, rounded, with 

 parallel sides ; dorsal sinus acute ; lateral sinus very large, mucronate. 



This species is much thicker, or more nearly spherical, than either the G. crenistria, G. obtus/is, or G. 

 striolatus ; from the first and second it difiers, besides its thickness, in the greater size of the umbilicus, and 

 width of the lateral lobes of the septa, and from the latter, by its large size, very long lateral sinus, short lateral 

 lobe, and spherical form ; from the G. spharicus it difiers in the short, wide, lateral lobes, longer lateral sinus, 

 and the absence of spiral stria;. Diameter one inch six lines, thickness one inch, diameter of umbilicus six 

 fines. 



