800 REPOET OF COMMISSIONER OF FISH AND FISHERIES. [54] 



upon the Teleostean type, and all the elements found in the bony 

 fishes are present. 



Mr. Bridge, in his figure (Jour. Anat., 1877, Fig. 6) representing what 

 I here have drawn in my figure 19, has inserted cartilage among the 

 palatine and the several x)terygoid bones. Tbis material I have failed 

 to find in this situation in any specimen of the age represented in either 

 figure that I have thus far examined. 



The palatine (PI. VI, Fig. 19, Fl.) is thoroughly well developed and 

 armed with two sets or kinds of teeth ; the first of these, and the larg- 

 est in this part of the skull, form a single row upon the lateral or exos- 

 teal i)ortion of the bone in continuation with thos'e on the premaxilla;. 

 Others, very much smaller, are arranged internal to these on the en- 

 dosteal lamina of the palatine and continue the vomerine series. An- 

 teriorly at its apex the palatine is grooved to receive the inturned pro- 

 cess of the maxillary, which is here wedged in between this bone and 

 the premaxillary. The palatine is also in relation in this region with 

 the septomaxillary, vomer, and prefrontal. It possesses the unique 

 character among Ganoids in its relation Avith the latter bone in being- 

 carried in front of its articulation, a condition well known to us among 

 the bony fishes. 



The entopterijgoid forms the major share of the floor of the orbit, ar- 

 ticulating b.v overlapping sutures with the bones it comes in contact 

 with, while its entire buccal surface seems to be overspread with very 

 minute teeth. This latter condition applies also to the ectopterygoid 

 (PI. VI, Fig. 19, Eii'pt. Ectp.)^ this bone being additionally armed with a 

 row of tine teeth upon its lower border containing the palatine series. 

 It connects the palatine and quadrate but is separated from the meta- 

 pterygoid by a thin strip of the entopterygoid. 



The metapterygoid (Fig. 19, M. Pt.) is shaped like a fau with its han- 

 dle, tipped on the end with cartilage, directed upwards toward the 

 orbit. This is the ascending process of the metapterygoid. The fan 

 part terminates in an angle at either extremity; the anterior angle 

 nearly touches the alisphenoid, while the posterior one overlaps the 

 hyomandibular. 



So close is the union between the quadrate and symplectic, that these 

 two elements appear to form one bone. Taken together they are shaped 

 somewhat like a spherical triangle, the lower angle of each being dis- 

 tinct, the symplectic terminating above the quadrate, each to bear an 

 articular facet for the mandible. In the case of the quadrate this is 

 convex and hemispherical, while in the companion bone it is crescentic 

 and concave, being in reality, one-third of the socket of which the preo- 

 perculum affords the remaining two-thirds. 



It requires severe maceration in order to separate the symplectic from 

 the quadrate, the union almost amounting to true anchylosis. 



The hyomandibular (Fig. 19, S. M.) is obliquely pierced by an ellip- 

 t^ical foramen, near its centre for the exit of the facial nerve. Above, 



