23 FISH OF THE CARBONIFEROUS PERIOD. 



crown coarsely punctured, a few of the punctures near the apex 



longitudinally confluent so as to give it a slightly pectinated 



appearance ; width of crown 2^ lines. 



Easily distinguished by its small size, coarsely punctured sur- 

 face and the raised lobe of the margin of the crown. 



Rare, in the limestone of Armagh, from whence there is one 

 example in the University collection at Cambridge, and another 

 in that of Capt. Jones. 



Glossodus (M'Coy), n. g. 



Gen. Char. Tooth tongue-shaped, oblong, quadrangular, much 

 higher than wide; crown elevated, slightly recurved, nar- 

 rowing from the base to a small, subtruncate apex ; surface 

 porous, puncta generally seeming confluent towards the apex ; 

 punctured surface terminating below in a notch, or arched 

 line, the convexity upwards ; root long^ as wide as the crown, 

 coarsely fibrous. 



The Ghssodi are distinguished from the Helodi, with which 

 alone they have any affinity, by the quadrangular form of the 

 horizontal section of the tooth, the sides being flattened as well 

 as the anterior and posterior faces ; also by the great height of 

 the crown in proportion to its width. The long root-like base of 

 the tooth, which resembles that of some Petalodi (e. g. P. psit' 

 tacmuSy Ag. MSS.), rather than that of Hehdus in form, is of an 

 open lacunose structure, being permeated by very large flexuous 

 medullary canals producing irregular openings on the surface. 

 The ridge separating the punctured surface from the base forms 

 a sinus directed upwards, which is the reverse of what we find in 

 Petalodus, approaching the ordinary sharks, and also conforming 

 to what we see in Helodus and Strophodus when the separating 

 line in those genera is not straight. As in Petalodus, the basal 

 margin of the surface is much nearer the apex on the convex an- 

 terior side than on the concave posterior or internal face, the 

 latter being generally about twice the length of the former. The 

 characters above given as distinguishing those teeth from the 

 Helodi also separate them from the genuine Petalodi of Owen, as 

 also the want of the imbricating folds at the base. 



Glossodus lingua-bovis (M^Coy). 



Sp. Char. Height of the crown exceeding the width of the base, 

 which is three times the width of the truncated apex ; greatest 

 antero-posterior diameter half the width of the base ; surface 

 dull, covered with coarse, wide, occasionally confluent puncta, 

 the interstices crossed by minute, flexuous, oblique striae. 

 This curious tooth resembles a neat's tongue in miniature ; 



