2 



BRITISH FOSSILS. 



gated scales, overlapping its base. Five or six of the upper fin rays are 

 much stronger than the succeeding ones, and have no transverse articula- 

 tions until near their extremities ; the remaining rays of the upper lobe, 

 and all those composing the lower lobe, have very frequent articulations 

 from the base to the extremity. The length of this specimen is oj inches 

 from the nose to the commencement of the caudal fin ; the depth from the 

 nape, 1 1 inches. The length of the head from the nose to the posterior 

 edge of the operculum, 2 inches. 



Article XI. Plate IX. and IX*. 



Oxygnaihus ornatus. — The fortunate discovery of a most perfect example 

 of this rare fish enables me to complete the description of those parts that 

 are either mutilated or wanting in the specimen originally examined. The 

 recent acquisition measures 11 inches from the snout to the fork of the 

 tail, and 3 inches in depth between the nape and the dorsal fin. The 

 position of the fish is such that all the fins of the left side are shown, and 

 by a lucky upturning of the lower jaw, both rami, together with the hyoid 

 and branchiostegous apparatus are displayed. The parts shown in this spe- 

 cimen, which were deficient in the former one, are the dorsal and caudal 

 fins. The more perfect condition of the anal fin renders some cor- 

 rection requisite in the description formerly given of this organ. It 

 is, in fact, not so small as I was led to suppose, but is in full proportion 

 to the other locomotive organs. It commences anteriorly with a few 

 graduated jointed rays, and not with the single fulcral rays frequently 

 found in this position ; these arc succeeded by the principal rays, about 

 30 in number, which decrease in length rapidly as they recede towards 

 the tail. The transverse articulations of the principal rays are frequent 

 near the base of the fin, but occur at greater intervals on the more distant 

 portion ; on the posterior rays they are also frequent, but uniform through- 

 out. The dorsal fin is situated immediately above the interspace between 

 the ventral and anal fins. It was furnished, like the anal fin, with a few 

 soft slender rays on the anterior margin, The succeeding rays corre- 

 spond also in size and character with those of the anal fin. In consequence 

 of a olight mutilation of the hinder extremity of the fin, the exact 

 number of the rays cannot be ascertained ; it was certainly not less than 30. 

 The most remarkable and wholly unexpected character of this fish is pre- 

 sented by the form and structure of the caudal fin. This organ is deeply 

 cleft into two lobes ; the upper one measures 3|- inches in length, the 

 lower one only 2-|. The former has a scaly investment from the base to 

 the extremity, below which issues a fringe of innumerable fine rays, with 

 frequent transverse articulations and longitudinal bifurcations. The lower 

 lobe contains about 24 rays ; of these the strongest occupy the middle of 

 the lobe, those of the upper and lower margins becoming gradually finer 

 as they recede from the centre. The transverse joints are nearly equi- 

 distant, but the intervals are greater than those on the dorsal and anal 

 fins. It results from these peculiarities that this fin in Oxygnathus not 



