570 RAMSAY n. TRAQUAIR ON AMBLYPTERUS, 



referable to the same species — and to Dr. Hunter, of Braidwood, for 

 the loan of a magnificent slab covered with its scales, bones, and fin- 

 rays from the shale underlying the " Main Limestone " (Lower 

 Limestone series) of that locality. All the specimens which have as 

 yet been found have been fragmentary, consisting only of detached 

 scales and bones, or of masses of scales either confused or adhering 

 together to some extent in their original rows. Dr. Hunter's slab 

 measures 20 inches in length by 11 in breadth. It displays, in the 

 first place, a number of bones the forms of such of which as are 

 determinable stamp the fish at once as a member of the family 

 Paloeoniscidce. Among these may be recognized the median supereth- 

 moidal, which in this family forms the anterior projection of the 

 snout over the mouth : and tying near it is the impression of a bone, 

 4 inches in length, which displays the characteristic form of the 

 Paheoniscid maxillary. No impressions of teeth are seen ; it is 

 therefore unfortunate that the counterpart of the specimen could 

 not be found, as the bony substance of the maxilla has evidently 

 remained on it, the teeth not having been exposed. The lower 

 portions of both clavicles are also seen ; and the dimensions of these 

 are such as to lead one to suppose that the length of each, when 

 entire, could not have been less than five or six inches. The external 

 ornamentation of all these bones is of a tubercular nature, the 

 tubercles sometimes finer, sometimes coarser, occasionally showing a 

 tendency towards a linear arrangement or to coalesce into short 

 ridges. 



Besides the numerous scattered scales which occur in the slab, 

 there are two large patches in which the scales still cohere together 

 in rows. One of these patches evidently represents a portion of the 

 skin of the front of the flank, the position of the other being further 

 back towards the caudal region. These flank-scales are large ; one 

 of the largest of them is || inch in breadth ; its exposed and ganoid 

 area is nearly equilateral, measuring about T 7 y inch in breadth and 

 in height ; this area is rhomboidal, but not acutely so, and is 

 obliquely traversed by strong subparallel ridges, which proceed in 

 a direction from above, downwards and backwards, occasionally 

 branching and anastomosing, or, where two diverge, another being 

 intercalated between, there being, on an average, five such ridges 

 in the space of ± inch. The anterior covered area overlapped by 

 the scale in front is extensive, being y\ inch in breadth ; its lower mar- 

 gin is more oblique than that of the sculptured portion, with which 

 it consequently forms an obtuse angle ; above it is produced into a 

 prominent pointed process, where it coalesces with the narrower 

 covered area of the upper margin, overlapped by the scale next 

 above. From the middle of the upper margin there projects, in 

 addition, the proper articular peg of the scale, stout and triangular 

 in form. Near these scales are scattered others which were evi- 

 dently situated towards the ventral aspect of the fore part of the 

 fish. These display a similar sculpture of the exposed area : but 

 their form is lower, narrower, and more oblique ; the articular peg 

 of the upper margin has disappeared : but the anterior superior pro- 



