ON DOKYPTEKUS HOFFMAKNI. 251 



upwards of four inches and a quarter in length, and is extremely- 

 narrow, being only two-tenths of an inch wide an inch from the 

 base, gradually tapers to a fine point above, and as gradually 

 widens downwards to within three-eighths of an inch of the base, 

 which suddenly expands, stretching forwards almost as far as 

 the occiput, and backwards to the root of the tail, as a narrow 

 fringe, similar in height and appearance to that on the opposite 

 or ventral margin. The anterior prolongation (<x") is composed 

 of a double lateral series of about twelve low, stout, pointed, 

 scale-like rays or processes, the fin-fulcra, inclining and increas- 

 ing in length backwards. The first of the series is extremely 

 short, just appearing above the dorsal ridge ; the last is about 

 four-tenths of an inch in length ; and the whole, leaning in the 

 direction of the fin, one supporting the other, form, as it were, 

 a sort of buttress to the base of the enormously elongated fin. 

 Only a few of the central rays reach to the top of this elongated 

 portion of the fin ; both in front and behind they die out gradu- 

 ally. At the base, just above the fin-fulcra, there are twelve or 

 thirteen rays ; halfway up they are reduced in number to seven 

 or eight ; and within half an inch of the top, judging by the up- 

 per portion of a fin in our possession, there are only four or 

 five. All the rays are divided into numerous and unusually 

 elongated joints (fig. 4), which at the points of articulation are 

 slightly enlarged. The joints are longest in the centre or ante- 

 rior rays, some of them measuring one-tenth of an inch in 

 length. 



The tail is distinctly heterocercal, and is deeply and regularly 

 forked, the upper lobe being only a little longer than the under. 

 The former is one and a quarter inch in length ; and from tip to 

 tip of the lobes the tail is one and a half inch in width. The 

 anterior margin of the upper lobe is defended by a closely ar- 

 ranged series of stout, sharply pointed, enamelled, scale-like pro- 

 cesses or fin-fulcra (fig. 1,/), which imbricate and diminish in 

 size backwards. Behind or below these there is a double row 

 of rhombiform scales (e), likewise covered with enamel, and 

 articulating lengthwise by notches and points. The fin-rays, 

 which occupy more than half the width of the entire lobe, are 



