64 MESSES. HANCOCK AND ATTHEY ON 



truncated. The mandibular bone is not much widened poste- 

 riorly, and is about half as long again as the tooth. 



The specimens vary much in size, the largest being a little 

 over 1^ inches long, while the length of the smallest is not more 

 than fths of an inch. The former has seven ridges, the latter 

 six ; so that it is evident that age does not make any material 

 change in this respect. This is highly satisfactory, as we can 

 with greater assurance assume that the number of ridges is a 

 good specific character. 



The anterior \ ortion of a fish of this species has occurred at 

 Newsham, exhibiting one of the gill-opercles and two of the den- 

 tal plates with the denticles interlocked; numerous scales are 

 also displayed, but they are in such a mashed-up state that the 

 characters cannot be determined with precision. Enough, how- 

 ever, is seen to show that they agree with those of C. elegans, 

 though the ridges or plaits ornamenting the surface are not so 

 numerous, and are considerably coarser ; the rosette, too, in the 

 centre of the exposed portion is not so conspicuous, and seems 

 to be smaller. The opercular plate, which is upwards of an inch 

 across its longer diameter, and a little more than fths of an inch 

 in the other direction, is thick and irregularly ovate, with the 

 margin sinuous ; the hinge -line is long, and has a slight projection 

 in the centre ; the surface is strongly punctured and granulated, 



5. Ctenodus elegans, n. sp. 



Tooth depressed, triangular, upwards of fths of an inch long, 

 and -j^ths of an inch broad ; the inner margin is produced and 

 angulated in the centre, whence it slopes in front and behind to- 

 wards the outer margin, which is gradually but slightly arched ; 

 the surface is provided with eight strongly denticulated ridges, 

 which radiate from the inner marginal angle, where they are very 

 minute, to the outer border; the anterior ridge is a little produced 

 at the outer margin beyond the rest ; there are six or seven den- 

 ticles or tubercles on each ridge ; they are much compressed at 

 the sides, are sharp pointed and lancet-like, with the inner limb 

 a little shouldered, where there is occasionallj^ a minute toothlet ; 



