74 Proceedings of the Royal Physical Society. 



margin of this fin measures 2| inches ; it has a narrow scaly 

 base, and expands somewhat distally ; its apex is bluntly 

 pointed. Opposite this, upon the ventral aspect, is the anal 

 fin, of the same length, but rather more lanceolate in shape. 



The pectoral fins are well shown in a specimen in my own 

 collection; they are short and obtusely rounded, with an 

 obtuse basal scaly lobe fringed with rays. The lobation of 

 the ventrals seems to be not quite so marked. 



All these fins are composed of numerous closely set rays, 

 divided by very close transverse articulations, except quite 

 at their proximal extremities, which are covered by the scales 

 of the body; they dichotomise towards their extremities, 

 and their free surfaces are brilliantly ganoid and punctated 

 like the scales. 



Scales. — The scales present the same appearance externally 

 as in M. Hihberti, and are not to my eye distinguishable. 

 Their internal surfaces are seldom seen, and appear some- 

 times furnished with the prominent keel seen in M. Hihherti, 

 while in other instances this appears to be absent. 



Vertebral Column. — A specimen in the Museum of Science 

 and Art shows the presence of ring-shaped vertebral centra 

 as in M. Hihberti. 



Head. — Fig. 3 represents, reduced in size, a very instructive 

 head in the Hugh Miller Collection, in which the cranial 

 shield is very well shown. This is as usual divided across 

 into two portions, an anterior or fronto-ethmoidal, and a 

 posterior or parietal, but in this instance the anterior portion 

 is longer by one-seventh than the posterior one ; iii M. Hih- 

 berti, on the other hand, the posterior moiety is the longer. 

 Taking the parietal part of the buckler, it may also be seen 

 to differ in shape from that in the ordinary species, in being 

 proportionally broader in front. The plates of which it is 

 composed seem pretty completely fused together as the 

 indications of their original separation are slight and princi- 

 pally posteriorly. Near the hinder margin are also seen 

 certain grooves like those observable in a similar situation 

 on the cranial shield of Osteolepis and Diplopterns. One of 

 these passes transversely across the middle of the squamosal 

 element : another is V-shaped, one leg of the V continuing 



