17 



sound abdominal vertebrae have no parapophyses, nor have they any pleurapophyscs eon- 

 neetod with them. Tin- (larapophyses begin to br deve loped from the lower part of the tide 

 of the centrum of thr third vertebra, and gradually increase in size to the tenth. They con- 

 tinue short and thick to the antepenultimate abdominal vertebra, suddenly increase in the 

 penultimate one, where they present a triangular form with an excavated base, project down- 

 wards and backwards in this and the last abdominal vertebra, and are united together by a 

 transverse bony bar across their lower extremities in the first caudal vertebra. In this and 

 the second they descend parallel with each other from the under surface of the centrum, 

 begin to converge in the third caudal, and unite together at an acute angle in the fifth ; the 

 spine beyond the union progressively increasing in length to the tenth caudal, and thence 

 slightly dimiuiahing to the twenty-fifth. This begins to increase both in length and antero- 

 postehor breadth. The hirnial arches in the succeeding caudal vertebrae arc joined by suture 

 to their respective centrums, increase in thickness and in autero-postcrior extent, and are 

 suturallr articulated together with a slight degree of imbrication. A ridge is developed from 

 each side of the base of the fourth of these three inverted arches. The six last contribute to 

 support the rays of the caudal fin, the rest being supported by the modified centrum of the 

 last caudal and by the neurapophyses of the five preceding caudal*. 



The pleurapophyses * are long and slender: they rapidly increase in length to the sixth, 

 and gradually diminish after the twentieth. Their proximal end is slightly expanded and 

 articulated to the parapophysis, to which they continue to be articulated after the |>ara|>ophyses 

 have bent down and united together to form the hicmal arch. There are thirty-two pairs, 

 the last pair being articulated to the sixth caudal vertebra. 



The iutenieural spines which form the basis of the dorsal fin are twenty-three in number, 

 and extend from thr fifth to the twenty-fifth neural spine inclusive : the ten anterior iiiter- 

 neural spines terminate freely ; the first is of moderate length, compressed, but expanded from 

 before backwards. This dimension decreases and the spine elongates, until it assumes the 

 form of a simple ray in the fourth. The thirteen posterior intemeural spines are expanded 

 and united together at their distal ends, where they articulate with fourteen dermonrural 

 spines or rays of the dorsal fin. These rays are essentially double, or consist of a pair, dis- 

 united though in contact in the first and second, but joined together at their distal portions 

 in the rest, where they are divided into several soft-jointed filaments in the last eleven rays. 

 Prom the first to the fourth of the dermoneiiral rays, these very rapidly increase in length ; 

 from the fourth they diminish, but less rapidly, to the last. From the end of the premaxil- 

 laries to the first dermoneural ray is 1 9 inches. From the origin of the last dennouriiral ray 

 to the first ray of the caudal fin is I'.'J inches. The small adipose fin is here preserved : 

 its base lies over the 1 8th caudal vertebra. The number of caudal rays is 34, of which 1 7 

 are attached to the neural spines ami the hut caudal vertebra, and 1 7 to the haemal spine*. 

 These Utter, however, form two-thirds of the straight vertical border of the caudal fin, in 

 consequence of their larger size. 



The ischial boon, which are joined by a thick cartilaginous srmphysis at the median line, 

 he underneath and parallel with the last six abdominal vertebrae. Each ischium support* 



These elements are the inferior cost* or ribs, umtere rippt ' of Mcckel. 



D 



