62 LECTURE in. 



pophyses, as in the cartilaginous Heptanchus, Carcharias, and 

 Alojjias. 



Between the floating ribs extends an aponeurosis, the remains or 

 homologue of the primitive fibrous investment of the abdomen in the 

 Lancelet and Lamprey. In the Salmon and Dory the ribs continue 

 to be attached to some of the parapophyses after they are bent down 

 to form the hjemal canal and spine in the tail ; and we derive the 

 same striking evidence of the true nature of these inferior arches 

 from tlie skeleton of the Tunny, the Dory, and some other fishes. The 

 costal appendages of the first vertebra of the trunk are usually larger 

 than the rest, and detached from the centrum ; at least if we regard 

 as such the styliform bones (^r/. 19. 58) which project from the inner 

 side of the scapulae, and which have been described as coracoids 

 (Cuvier) and sometimes as displaced iliac bones (Carus). By the mus- 

 cles attached to these styliform bones the succeeding ribs are drawn 

 forwards and the abdomen expanded in the Cyprinoids. Pleura- 

 pophyses are entirely absent in the Sun-fish, Globe-fish (Diodon), 

 the Tetrodon, the Pipe-fish (Fistularia and Syngnathus), the Lump- 

 fish and the Angler. This of all osseous, or rather semi-osseous, 

 fishes presents the sirnplest vertebral column : the abdominal ver- 

 tebrai are not only devoid of ribs, but have the feeblest rudiments 

 of parapophyses. The bodies of these vertebrsE interlock at their 

 lower and lateral parts by a short angular process fitting into 

 a notch in the next vertebra ; the lower border of this notch repre- 

 sents the lower transverse process in other fishes : it is obsolete in 

 the anterior abdominal vertebrae ; begins to appear about the middle 

 ones ; shows its true character in the tenth ; and elongates, bending 

 downwards, backwards, and inwards, to coalesce with its fellow, and 

 form the hoamal arch at the twelfth or thirteenth vertebra, from 

 which the htemal spine is developed. The interlocking process of 

 the anterior vertebra disappears as the true inferior transverse 

 process is increased. The side of the neural arch is perforated for 

 the nerve, and that of the hasmal arch for the blood-vessel.* The 

 anterior abdominal vertebrte of the Tetrodon are more firmly clamped 

 together by the parapophyses than in the Angler. 



A vegetative sameness of form prevails in Fishes throughout the 

 vertebral column of the trunk, which is made up of only two kinds 

 of vertebrae, characterised by the direction of the parapophyses : 



* The gclatino-cartilaginous basis is progressively but continuously ossified 

 around tlieso foramina, which form part of a vast series of exceptions to the so- 

 called " loi de conjugaison" of M. Serrcs ; who, by this phrase, expresses his notion 

 that every foramen is formed, like those that give passage to the spinal nerves in 

 Mammalia, by the approximation of two notches of two distinct bones or bony 

 elements. 



