16 SYNOPSIS OF THE CHARACTERS OF THE 



GONIATITES SPIRALIS. Phil. 

 Goniatites spiralis. Phil. Pal. Fos Goniatites granosus. Portk. Geol. Eep. 



Sp. Ch. — Discoid (compressed?) umbilicus very small, rounded; surface, with numerous close, equal, finely 

 crranulated, spiral striae, the spaces between which are transversely striated. 



All the specimens of this shell which I have seen were quite flat from compression, and I am not aware 

 of the true proportion which the thickness should bear to the diameter, nor have I seen the septa. Diameter 

 usually about two inches. 



Goniatites steiatus. Sow. sp. 



Ammonites striatus. Sow. Min. Con. — Goniatites striatus. Phil. Geol. York. 



Sp. Ch. — Spheroidal, slightly depressed, finely striated longitudinally ; umbilicus small, rounded, with an 

 obtuse margin ; septa, dorsal lobe bifid ; dorsal sinus angular, acute ; first lateral lobe angular, acute, rather 

 more than twice the length of the dorsal lobe ; second lateral lobe blunt, shorter than the first lateral lobe ; late- 

 ral sinus angular, acute, not longer than the dorsal sinus. 



This species is known at once from the G. sphcBricus, by its more compressed form, and acutely angular 

 first lateral lobe. Both these species exhibit variable internal ridges on the cast. Diameter two inches, thick- 

 ness one inch. 



Goniatites steiolatus. Phil. 



Goniatites striolatus. Phil. Geol. York. 



Sp. Ch. — -Subglobose ; sides slightly convex, gently sloping towards the back, which is narrow, rounded; 

 umbilicus large, acute-edged ; surface with fine, rather distant, straight, transverse striae ; septa, dorsal lobe 

 very short, bifid ; dorsal sinuses wide, pointed ; lateral lobes large, obtusely rounded ; lateral sinus moderate, 

 mucronate. 



This pretty species differs from the young of G. ahtusus, by having the back narrower, and the sides 

 sloping towards it, not parallel, its larger umbilicus, and more obtusely rounded first lateral lobe. Diameter 

 about one inch, thickness five lines. 



Goniatites teuncatus. Phil. 



Goniatites truncatus. Phil. Geol. York. 



Sp. C/i.— Discoid, compressed ; sides flattened ; back flat, or sHghtly convex, meeting the sides nearly at 

 right angles ; umbilicus very small ; surface with very fine transverse striaj. 



Resembles the G. ohtusus, but easily distinguished by its more compressed form, flatter sides, and flat, 

 truncate back. Diameter one inch and a half, tliickness six lines. 



Goniatites vittiger. Phil. 



Goniatites vittiger. Phil. Geol. York. 



Sp. C/«.— Discoid, compressed, smooth; sides convex, concave towards the keel; back with a large, 

 square keel ; umbilicus wide, shallow, exposing the edges of the whorls ; whorls five or six. 



I have not yet seen the septa of this curious shell ; it resembles a Spirorbis when one side only is seen. 



