ICHTIIVOLOGY OF THE LBSSER ANTILLES. 



447 



Polypterus. In Lepidosteus and Amia, wo have the doublo ceratohyal, four braiioliiliy.il arches with four outer and 

 four inner superior elements, all characters of tho typical Teleostei. The maxillary bone of Polypterus instead of 

 being free distally as in fishes generally, is united with an ectopfcorygoid, and with bones representing, in position 

 at, least, postorbital and malar. \n tho other genera, the relations of the maxillary are as in osseous fishes. 



The sturgeons, AccipenseridcB, agree with Amia, etc, in all of those points but one, differing only in having the 

 superior ceratohyal and several of Urn superior branchihyals cartilaginous. Tho ono point of distinction is, tho ex- 

 tension of tho basal radial supports of the ventral fin all across its basis, as in Polypterus. Tho pectoral fin is, on 

 the Other hand, much as in Lepidosteus. Thus tho sturgeons combine, in this ono respect, the features of both 

 divisions. Both the basal ooratoliyals are cartilaginous in this family; the superior only is cartilaginous in Polyp- 

 terns, Lepidosteus and Amia, while both are ossified in the old Teleostei, except in tho ools. In these, tho inferior is 

 cartilaginous, while the superior is ooossifiod to tho oeratohyal. Thus in ono unimportant character Polypterus 

 agrees with its former associates, but dififers more from others of them, the sturgeons, than from the bony fishes. 

 Another charaetor of both Lepidosteus and Amia betoken a certain relationship to Polypterus, viz.: the complexity 

 of tho mandible, especially in tho possession of a coronoid bono. But here, again, Accipenser only possesses an 

 osseous dentary, while Gymnare7ms and Oymnotus have the angular and articular bones distinct from tho dentary, 

 wauling the coronoid and opercular. In most bony fishes tho angular is not distinct. 



It is thus evident that the sub-class Ganoidea, cannot bo maintained. It cannot even be regarded as an order, since 

 I will show that Lepidosteus, Accipenser and Amia, are all representatives of distinct orders. I hope also to make it 

 evident that Polypterus should be elevated to the rank of a sub-class or division of equal rank with the rest of the 

 fishes, and with the Dipmoi already adopted. 



8. Relations to otheb Vbbtebeata, 



The primary divisions of the verlebrata as expressed by tho skeleton, have been defined by Huxley in a very satis 

 factory manner, up to a certain point. Thus the MAMMALIA are distinguished by the reception of the proximal bones 

 of the mandibular aroh into tho auditory capsule, as ossioula auditus, and by tho absence of distinct ooracoid bono. 

 The ear hones support tho under jaw in the groups that follow, and a separate coracoid bono exists. Tho division of 

 birds and reptiles together, or SAUEOPSIDA, possesses limbs with but few and special radii, an osseous basis cranii, 

 without parasphenoid bono, and one aorta roof or two of ono bow on each side (rarely a second bow). The division 

 iii' m I below, or Batbachia, was shown to possess no osseous basis cranii, whoso place is taken by tho membrane bows, 

 the parasphenoid: limbs with but lew radii, and an aorta originating from two roots, attached to which are three or 

 four bones on each side. 



following these, is the great group of fishes, in which the limbs arc many rayed or jointed, or fins ; a parasphenoid 

 present, and pelvis generally wanting. The stapes, which has not in tho preoeding groups shared in the support 

 of the mandible, is now projected from tho brain case so as to share with tho malleus (quadrate) in this support, being 

 still tho proximal element in the hyoid arch, as in the preceding classes. There are five (rarely four) aorta bows 

 which unite to form the aorta root on each side. The cranium is cartilaginous or osseous, and the mandibular arch 

 present. Below these come the Demoptebi, where the limbs arc wanting, and the mandibular aroh absent: the 

 cranium cartilaginous. In the lowest group or Leptocaedii, there is no differentiated brain, the cranium is mem- 

 branous and without arches : limbs wanting, and five aorta bows as in the last division. 



These six classes of vertebrata appear to be well established. The question remains as to whether naturalists 

 are correct, who regard the fishes as representing variously from two to four classes. One of these (the Ganoidea) 

 having been already disposed of, it remains to consider tho claims of the remainder, viz. : the Elasmobranohil (sharks) 

 Dipnoi and typical fishes. 



If wo examine the points in which tho whole, taken together, differs from the BatraeMa and other classes above 

 it, wo find that if is oonfined chiefly to tho structure of the limbs and tho hyoid apparatus. The typical fishes pre- 

 sent, howover, other important peculiarities, viz. : 1st. The existence of two or throe distinct bones in tho suspensor 

 of the mandible, instead of one ; 3d. The attachment to those of tho opercular bones ; 8d. Tho absence of pelvic 

 hones; 4th. The suspension of the scapular arch to the cranium ; 5th. The large development of the ptcrotic (Par- 

 ker, Mastoid, Cuvicr, and Owen) is characteristic of bony fishes, 



