Dr. R. H. Traquair — On the Genus Megalichthys. 119 



dorsal, while opposite the second dorsal is an anal fin of moderate 

 size, but whose rays are unfortunately rather broken up. The 

 caudal is pretty well shown, but not so well as in the next specimen, 

 in which the form of the tail and of the second dorsal and anal are 

 exceedingly well displayed. Fig. 2 represents the caudal extremity 

 of this specimen, which is 14 inches in length, but originally it must 

 have been considerably longer, as it wants the head, and I should 

 imagine also a good bit of the body. The caudal fin here shown 

 may be said to be somewhat intermediate between the dipliycercal 

 and heterocercal types, at least it is not quite so heterocercal as that 

 of Osteolepis, and in general form reminds us of that of Tristichopterus. 

 Eays arise from both the upper and lower margins of the body- 

 continuation, bat those of the lower side commence in advance of 

 those of the upper. After the commencement of the rays, the upper 

 margin of the body-prolongation slopes very little downwards, while- 

 on the other hand the lower one slopes very rapidly upvvards ; the 

 two margins then converge to a point which is lost among the fin- 

 rays, the scaly covering being lost at this part. The posterior 

 margin of the fin slopes obliquely upwards and backwards, the 

 greater number of the rays arising from the lower aspect of the body- 

 prolongation, while the apex, cut off in the specimen, would seem to 

 be formed by rays arising from the upper or dorsal side of the axis. 



On the dorsal aspect of the specimen, and just in front of the 

 caudal, is the second or posterior dorsal fin. The anterior margin of 

 this fill 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 collec- 

 tion : 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 raj^s, 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. Hibberti, and are not to my eye distinguishable. Their internal 

 surfaces are seldom seen, and appear sometimes furnished with the 

 prominent keel seen in M. Hibberti, while in other instances this 

 appears to be absent. 



Vertebral Gohimn. — A specimen in the Museum of Science and Art 

 shows the presence of ring-shaped vertebral centra, as in M. Hibberti. 



Head. — Fig. 3 represents, reduced in size, a vei'y 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 in M. Hibberti ; on the other hand, the posterior moiety 

 is the longer. Taking the parietal part of the buckler, it may also 



