Remarks on the Genus IMegalichtliys (Agassiz), etc. 73 



which may be noticed is one in the Edinburgh Museum 

 (Hugh Miller Coll.), which is pretty entire though small (PL 

 IV., Fig. 1). It measures lOf inches in length, though it must 

 be noted that the rays of the caudal fin are somewhat frayed 

 and broken at their extremities : the greatest depth of the body 

 is If inch ; the length of the badly preserved head is 2| 

 inches. The pectoral fin is not shown, but all the others are, 

 though perhaps not in so complete a state of preservation as 

 might be wished. There are two dorsal fins, of which the 

 anterior one is the smaller, and commences 6^ inches from 

 the front, while the second arises 1^ inch further back. The 

 ventral arises opposite a point rather behind the origin of the 

 first 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 diphycer- 

 cal and heterocercal types, at least it is not quite so hetero- 

 cercal as that of OsteoleinSy and in general form reminds us 

 of that of Tristichojjterus. Eays arise from both the upper 

 and lower margins of the body-continuation, but 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 upwards, 

 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 



