THE DEVONIAN ROCKS OP CANADA. 81 



and of a considerable portion of the so-called praeoperculum are well exhibited in this 

 specimen. 



No. 4. — This specimen, -which is represented in oiitline on Plate YI, is a nearly- 

 perfect example (though considerably distorted by lateral but slightly oblique compres- 

 sion) of a fish -which measures about sixteen inches from the tip of the snout to the outer 

 termination of the fin rays of the tail. All the unijaired fins and the paired fins of one 

 side are -well she-wn in place, though the facial bones of that side of the head -which 

 haj)pens to be exposed are not very -well preserved. There are f-wo large teeth in the 

 lo-wer jaw, as well as many small ones, and in this specimen the apophysis of the first 

 dorsal is barely one inch in length, and of correspondingly slender proportions as com- 

 pared with that of No. 1. 



No. 5. — Another well-preserved fragment, consisting of the whole of the tail, with the 

 tips of the anal and second dorsal, of an apparently half-grown individual, which, when 

 entire, was probably of about the same size as No. 4. This fragment is of special interest 

 as shewing the narrow and acute prolongation of the scaly portion of the body far up 

 into the central lobe of the tail, a character which is not seen at all in most of the other 

 specimens and only very indistinctly in No. 4. 



No. 6. — In this specimen, an outline of which is given on Plate Y, fig. 5, the greatest 

 length of the fish is seven inches. The general contour of the whole of the body, as well 

 as the exact shape and relative iiosition of all the unpaired fins and of the paired fins of 

 one side, are remarkably well shewn, but the head is not at all well preserved. 



General Shape and Proportions. — These, as already remarked, are best shewn in 

 specimen No. 6, which, however, is obviously very immature. At this stage of growth 

 the lateral outline is narrowly subfusiform, the head is obtusely pointed and occupies a 

 little loss than one-fourth of the entire length, the body is slender, its dorsal and ventral 

 margins being nearly straight and parallel from immediately behind the head to the 

 commencement of the first dorsal and ventrals, after which there is a gradual but 

 irregular narrowing of both these margins towards and into the tail. The maximum 

 length is more than four times, but less than five times, the greatest height. The first 

 dorsal is triangular in outline and placed a little behind the midlength, as well as 

 almost immediately opposite the ventrals. The second dorsal is longer aud more acutely 

 pointed than the first, the former being situated a little in advance of the anal and much 

 nearer to the upper lobe of the caudal than to the basal termination of the first dorsal. 

 The fin rays of the tail are divided into three distinct lobes, the two outer ones being 

 slightly convex on their outer margins and faintly concave on their inner, the extremities 

 of both being rather acutely pointed. The central lobe is rather more obtusely pointed 

 than the two lateral lobes, and both of its lateral margins are slightly convex. The 

 central lobe, also, is almost exactly equidistant from the upper and lower lobes of the 

 tail, and not placed much nearer the upper lobe, as in Dr. Traquair's restoration of 

 Tristichopterus. The anal fin, which is placed close to the lower lobe of the tail, is of 

 very nearly the same shape as the second dorsal, though not quite so large, and the 

 ventrals are similar in size and shape to the first dorsal. The pectorals, at least at the 

 stage of growth indicated by No. 6, are slender and longer than the ventrals and first 

 dorsal, as well as apparently rounded at their apices. 



Sec. IV, 1888. 11. 



