THE SKULL OF OSSEOUS FISHES. 127 



fishes in the geological formations anterior to the chalk are abdominal, 

 that is, have the ventral fins near the posterior end of the abdomen*, 

 we may conclude that the supporting bones are, essentially, the haa- 

 mapophyses of the last rib-bearing (or pelvic) abdominal vertebra ; 

 and that the rays are the diverging appendage, but are attached, 

 like the branchiostegal rays of the hyoidean (parietal haemal) arch, 

 without the intervention of fewer short and broad bones, homo- 

 logous with femoral, tibial, tarsal bones, &c. The hasmapophysial 

 portion (pubis) of the pelvic arch is never joined to the pleu- 

 rapophysial portion (ilium) of the same arch in fishes ; but is 

 suspended more or less freely to other parts, always projecting from 

 the under or ventral part of the body, but subject to great diversity 

 of position in relation to the two extremes of the abdomen. On these 

 differences Linnseus based his primary classification of fishes : he 

 united together, for example, those fishes which have the pelvic or 

 ventral fins near the anus, to form the order called " Pisces Abdo- 

 minales ;'" those with the ventral fins beneath the pectorals, into an 

 order called " Pisces Thoracici ;" and those with the ventrals in ad- 

 vance of the pectorals, into an order called " Pisces Jugulares ;" 

 lastly, those fishes in which the ventral fins are absent formed the 

 order called " Pisces Apodes." And by this name it will be ob- 

 served that Linnaeus recognised the special homology of the radiated 

 appendages of the pelvic arch of fishes with the hinder or lower 

 extremities of the higher classes of animals. 



In the Angler {Lophius piscatorius) each pelvic bone is attached to 

 the under and near the fore part of the long coracoid, expands at the 

 opposite end, and bends inwards to meet its fellow at a kind of sym- 

 physis pubis ; the fin, supported by six rays with expanded imbricated 

 bases, diverges from the angle ; and the suspending branch above this 

 seems to represent an iliac bone. The pubic bones are detached from 

 the coracoid arch in Abdominal Fishes ; the Thoracic character de- 

 pends upon the peculiar length of those bones, which carries back the 

 ventral fins to beneath the pectorals. As the ventral fins are always the 

 last to be developed in the embryo abdominal, thoracic, and jugular 

 fishes, so the apodals may be regarded as analogous to permanent em- 

 bryo forms of these fishes, in which development has been arrested be- 

 forearriving at the abdominal stage, and growth has proceeded, in most 

 cases, to excess in the linear direction ; as is exemplified in the Eel 

 tribe, where vegetative repetition of a vast number of incomplete 

 vertebrae has taken the place of the perfection of part of a fewer 

 number of vertebrte. 



* Agassiz, Hist, des Poissons, t. i. p. 105. 



