[75] THE OSTEOLOGY OF AMIA CALVA. 821 



is found in Perca^ and the arches in this latter fish have become so well 

 known both to layman and ichthyotomist, through the many reproduc- 

 tions made of Cuvier's old figure, that I have not thought it necessary 

 to present a figure of this part of the skeleton to illustrate our subject. 

 In the siJecimen of the bass in my hand, I find but two of the copuhie or 

 basibranchials ossified. We remember that three of them ossify in the 

 perch. Then follow on either side the five pair of segmented branchial 

 arches common to the vast majority of the class ; these bear the deutig- 

 erous patches on their ui)per surfaces — the gill-rakers being found 

 farther back and on the outer pair only — while below they support the 

 gills proper. 



My collection contains specimens, however, where all three of the 

 basibranchials are well ossified, and teeth appear on the upper surface 

 of the rear one in two circular patches. The ultimate gill-raker is T- 

 shaped, the horizontal bar being applied to the outer side of the arch. 



The outer jjair of branchial arches are each in two segments — a long, 

 posterior, and interiorly grooved pair, and an anterior or shorter pair 

 that articulate with the middle of the indented sides of the mid-basi- 

 branchial. These latter are bent at a right angle, the long limb being 

 continuous with the hinder segment; the short one, which is quite 

 broad, is the j)art that meets the basibrauchial. This description an- 

 swers very well for the second branchial arch. The anterior segments 

 of the third arch are much broader, and lie on either side of the iilti- 

 mate basibrauchial, while the fourth arch has no anterior segments; 

 the posterior ones, or those that correspond to them in the other arches, 

 touch each other in the median line. 



The infrapharyngeal hones are broad, thickly studded with teeth on 

 their superior surfaces, and drawn out into sharp extremities behind. 

 Supported in the usual manner through the means of ligaments by the 

 upturned portions of the arches, and lying beneath the cranium — the 

 suprapharyngeal bones — are also thickly beset with teeth. 



OF THE MANDIBLE OF MICROPTEBTJS. 



We saw that the lower jaw of A7nia ossified on either side from quite 

 a number of centers; that it developed a large splenial and other sep- 

 arate elements. This is not the case, however, with the large-mouthed 

 black bass. In this fish, as in many other Teleosteans, each ramus is 

 composed in the adult of but three distinct pieces. These are the den- 

 tary, the articular, and the angular (Plate III, Fig. 15, D. Art. and 

 Aug.). Owen tells us that "in both Sudis and Lepidosteus there is 

 superadded a small bony piece, answering to the surangular of Eeptiles." 

 (Anat. Yerts, vol. i, page 123.) 



The articular of Micropterus {Art.) consists of a vertical and a horizon- 

 tal portion, the latter being attached to its posterior half, and is ex- 

 tended backwards to bear the concave lunar facet to articulate with the 

 quadrate. The articular surface of this facet, although on the hori- 



