12 FISH OF THE CARBONIFEROUS PERIOD. 



the broken distal extremity being three lines wide, which would 

 probably indicate a further inch and half of length. The portion 

 of the base inserted in the flesh is small and gradually tapering. 

 I am not certain of the exact form of the section. 



Not uncommon in the red limestone of Armagh. 



{Col. University of Cambridge and Capt. Jones, &c.) 



Gyracanthus obliquus (M'Coy). 



Sp. Char. Dorsal ray nearly straight, about one foot long and 

 one and a quarter inch wide at base ; section heart-shaped, 

 width two-thirds of the antero-posterior diameter ; anterior face 

 narrow, rounded; posterior face broad, concave, having near 

 the apex a row of small hooked teeth on each side ; sides 

 slightly convex, marked with numerous very oblique crenu- 

 lated ridges or rows of tubercles, which meet the anterior face 

 at an angle of about 35° (those of opposite sides meeting at an 

 angle of 70°) ; the ridges become gradually more oblique, 

 smooth, and entire near the apex, they are about half a line in 

 width, and slightly more than their own diameter apart. The 

 line of separation between the ridged external surface and the 

 finely striated part which enters the flesh is very oblique and 

 with a slight sigmoidal curve. 



This large ray is most allied to the G, tuherculatus (Ag.), from 

 which it is distinguished by the much greater obliquity of the 

 sculptured ridges, and the more compressed form of the section ; 

 the G. Alnvicensis (Ag.) has ridges nearly as oblique as the pre- 

 sent species, but they are smooth and entire instead of being 

 strongly crenato-tuberculate. 



Very common in the dark shale (at the base of the carbo- 

 niferous system), supposed to be of the age of the yellow sand- 

 stone, in the valley of the Moyola, at Moyheeland, Draperstown, 

 in the N. of Ireland. 



{Col. Cambridge University and Mr. Griffith at Dublin.) 



Physonemus arcuatus (M'Coy). 



Sp. Char. Ray wide, much curved ; longitudinal rounded ridges 

 very numerous, about fifteen in the space of half an inch, less 

 than their own diameter apart, dilated into rounded, smooth, 

 bubble-like tubercles, which are nearly twice their diameter 

 apart ; the narrow sulci between the ridges have two or three 

 obscure longitudinal striae. 



Distinguished from the Physonemus subteres (Ag.) by its much 

 greater size, more numerous ridges and wide arcuate form. 

 Very rare : from the carboniferous limestone of Armagh. 

 {Col. Cambridge University.) 



