14 FISH OF THE CARBONIFEROUS PERIOD. 



mation are made available to those studying the subject, that we 

 are mainly indebted for the extended lists which have been pub- 

 lished of the Ichthyolites of this formation. 



Erismacanthus Jonesii (M'Coy). 



Sp. Char. Posterior spine little more than twice as long as wide, 

 slightly curved, compressed, sides flattened, with about eight 

 or nine longitudinal ridges, which are smooth and less than 

 their own diameter apart ; the intervening spaces finely striated 

 longitudinally ; posterior concave face with two regular, close 

 rows of small pointed teeth directed very obliquely downwards ; 

 the surface towards the base is marked with small, scattered, 

 oval, smooth tubercles ; anterior branch three times as long, and 

 about the same size at its origin as the posterior spine ; the part 

 of the spine from which those two portions take their common 

 origin is equal to the width of their united bases, and covered 

 with scattered round tubercles; the height of the anterior 

 branch is double its width at the basal half, but it becomes 

 depressed, so that its width is double the height in the section 

 of the distal half; it is covered above and on the sides with 

 close quincuncially arranged, smooth, oval tubercles ; the com- 

 pressed, finely striated base which enters the flesh seems 

 abruptly truncated below. Length of posterior spine 1 inch, 

 width at base 6 lines ; length of anterior process (imperfect at 

 extremity) 2 inches 9 lines, depth at base 4 lines, at tip 1 line ; 

 width at base 2 lines, at tip 3 lines ; length of the common 

 base 1^ inch, width 9 lines. 



Not very uncommon in the carboniferous limestone of Armagh. 

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



Cosmacanthus carbonarius (M^Coy). 



Sp. Char. Spine nearly straight, semicylindrical ; section semi- 

 lunate ; sides and anterior face broadly rounded in one conti- 

 nuous curve ; posterior sulcus very wide, rounded ; about eight 

 longitudinal rows of small oval tubercles on each side, the 

 tubercles nearly touching in each row, and the rows less than 

 their diameter apart ; no posterior teeth, the posterior sulcus 

 being bounded by the last lateral row of tubercles on each side. 

 A fragment 1 inch 8 lines long and 2^ lines wide at the nar- 

 row end, increases at the rate of nearly 2 lines in an inch. 



This difi'ers from the Devonian C. Malcolmsoni (Ag.) in its 

 greater size and much more numerous rows of tubercles. Two 

 imperfect specimens from the limestone of Armagh are in the 

 collection of Capt. Jones at Dublin. 



