CARBONIFEROUS FOSSILS OF IRELAND. 17 



Clymenia. Miinst. 



Endosiplionites. Ansted. 

 Gen. Ch. — Discoid involute; septa with one forward bend on the back ; siphuncle ventraL 

 This genus Is very distinct from Goniatites, by its ventral instead of dorsal siphuncle, and the comparative 

 simplicity of the septa. There is an undetermined species common in the limestone of Gregg Nobber, resem- 

 bling the C. IcBvic/ata, but with fewer, and more compressed whorls, and rounded back, without keel. 



Cltmenia plurisepta. Phil. 



Clymenia plurisepta. Phil. Pal. Fos. 

 Sp. Ch. — Discoid (smooth ?) umbilicus large, edge rounded; sides very slightly convex; thickness rapidly 

 diminishing from the edge of the umbilicus to the back, which is narrow, rounded ; septa about one line apart. 

 Diameter one inch, thickness half an inch. 



Clymenia sagittalis. Phil. 



Clymenia sagittalis. Phil. Pal. Pes. 

 This species differs from the last principally In being more compressed, and having a much smaller umbi- 

 licus. 



Fig. 8. 



DisciTEs. Jf' Coy. 



Gen. Ch. — Shell discoid, whorls exposed, quadrangular; back flat or concave; septa 

 concave outwardly, with an acute sinus at each of the latero-dorsal angles, and a deep, 

 rounded, dorsal sinus on the back, the concavity towards the mouth ; siphuncle towards 

 the dorsal margin. 



This genus is distinguished from all others of the family by the quadrangular form of 

 the whorls, these are all exposed, and are more numerous and more nearly equal in size than 

 In any of the other genera ; the angle formed by the meeting of the flat side with the flat or 

 concave back, produces a long, acute, lateral sinus In the edge of the septa, reminding us of 

 Clymenia, the point directed towards the mouth ; between these on the back, there is a large 

 obtuse sinus, the concavity of which is towards the mouth (fig. 8). The siphuncle Is dorsal, 

 or neai'ly so. 



Nautilus (Discites) costellatus. M'Coy. (PL II. fig. 4). 



Sp. Ch. — Discoid, inner whorls exposed; volutions very convex ; back rounded; umbilical edge steep, 

 smooth, whorls ornamented with about nineteen narrow, equal, prominent longitudinal ridges, separated by a 

 space rather greater than twice their own diameter ; septa very convex ; siphuncle central. 



This species is easily distinguished by the width of its volutions, broad, rounded back, and few dis- 

 tant longitudinal ridges; the number of whorls is about four; the width of the mouth from side to side is rather 

 greater than the length from before backwards ; the volutions are almost wholly exposed In a steep, smooth, 

 umbilicus, the spaces between the ridges on the surface appear nearly smooth to the naked eye, but under the 

 lens are seen to be marked with very fine transverse retroflexed strije. Diameter one inch four lines ; width of 

 mouth eight lines, length six lines. 



Nautilus (Discites) discors. M'Coy. (PI. Ill fig. 5). 



Sp. Ch. — Discoid, compressed, whorls five, entirely exposed, quadrate, back convex, equal in width 

 to the sides exclusive of the umbiUcal slope, sides shghtly flattened, evenly convex ; surface of the young shell 



E 



