of the Carboniferous Period. 121 



minutely and irregularly tuberculated ; two rows of small 

 conical teeth on the posterior margin, and two rows of larger 

 adpressed teeth on the anterior face directed upwards. 



The spines for which I propose this name are easily recognised 

 by their small size, curved form, and having the anterior, as well 

 as the posterior, margin armed with rows of teeth. These cha- 

 racters, while they separate them widely from the other fossil 

 spines, strongly recall to our mind the Pitnelodes and Synodonts of 

 the Nile ; in fact the Synodontus serratus described by Riippell* is 

 a perfect prototype, in its spinous defences, of our Dipriacanthus 

 falcatuSy except that both the anterior and posterior rows of teeth 

 are single on the recent spines. In their compressed section and 

 irregularly tuberculated surface the Dipriacanths resemble the 

 Oracanths, but are distinguished by their arched figure and rows 

 of teeth. 



Dipriacanthus falcatus (M'Coy). 



Sp, Char. Spine slender, gradually tapering, much hooked, com- 

 pressed, sides convex ; section oval, long diameter twice the 

 length of the short diameter ; surface with very minute irre- 

 gular, longitudinal strise, and few distant, irregularly scattered, 

 small tubercles ; teeth of the posterior margin short, conical, 

 at right angles to the spine ; teeth of the antei'ior margin, 

 slender, pointed, adpressed close to the spines with their points 

 upwards. Length of specimen imperfect, at base 1 inch 2 lines, 

 greatest width 2 lines. 



The specimen described is from the carboniferous limestone of 

 Armagh. 



[Col Capt. Jones, R.N.) 



Dip7'iacanthus Stokesii (M'Coy). 



Sp. Char. Slightly arched, much compressed , sides flat, anterior 

 and posterior margins narrow, obtusely rounded ; section ob- 

 long, the long diameter being from four to five times longer 

 than the short ; teeth of the posterior margin slender, conical, 

 projecting at right angles to the spine ; teeth of the anterior 

 margin large, thick, smooth, the upper sharp edge widest, 

 closely adpressed to the surface ; surface closely covered with 

 small, irregular, smooth granules, which under a strong lens 

 are found to be radiatingly striated at their base, and with the 

 intervening narrow spaces very minutely granulated. 



When highly magnified the granulation of this spine resembles 

 on a small scale the star-like style of ornament of the bony plates 



* Beschveibung und Abbildung mehrere neuer Fische, im Nil entdeckt, 

 Frankfort a. M. 1829, pi. 2. fig. 1. 



