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2 
THE OSTEOLOGY OF AMIURUS CATUS. 283 
valuable suggestions. His paper coming to hand after the previous 
descriptive portion had been written, explains the homology of the 
cavity described as occurring in the upper surfaces of the pterotic, 
supraoccipital, and epiotic. He shows that a similar cavity, which 
he terms the temporal cavity, occurs in Amia between the bones and 
the primordial cartilage, is widely open behind, and contains a _por- 
tion of the lateral musculature. In all probability the cavity in 
Amiwrus is a rudiment of this temporal cavity of Ama, the original 
contents of which have vanished, their place being taken by fat and 
blood-vessels. 
The same author suggests that the occipital segment of the Teleosts 
has fused with it a certain number of vertebre. He bases his asser- 
tions on the presence of such vertebre, partially fused, in Ama, 
Polypterus, Protopterus and Lepidosteus. If such be the case, there 
is no trace of such a coalescence in Amiwrus. A nerve certainly 
does pass out from the exoccipital behind the vagus, but in all its 
relations it is a spinal nerve, passing through the arch of the pre- 
ceding vertebra, as do the succeeding nerves. ‘The occipital segment 
is certainly composed of many segments, one corresponding to each 
branchial branch of the vagus and to the glossopharyngeal, but 
beyond these there is no indication of any further segments in the 
basioccipital of A mewrus. 
Il.—PALATO-QUADRATE AND MANDIBULAR APPARATUS. 
Under this head will be included a description of the maxillary 
and palatine apparatus, as well as of the chain of bones constituting 
the first postoral arcade, or, according to views expressed elsewhere,! 
the third cranial arcade, the trabecule cranii being considered as 
representing the first arch, and the palatine as the second. 
1. THe PreEMAXILLA, (Pl. II., Fig. 1, Pm.) 
Each is a small, somewhat arched bone, supporting five or six rows 
of teeth. They meet in the middle line, but are not united by suture, 
The upper surface of each bone rests on the under surface of the 
mesethmoid, and at the outer extremity each articulates with the 
maxilla. 
2. Tue Maxiuia, (Pl. I1., Fig. 1, Mz.) 
Depart very widely from the typical form. They are very much 
elongated rods, projecting at right angles to the sides of the skull, 
1.On the Osteology and Development of Syngnathus Peckianus,(Storer). Quart. Journ, Micr. 
Sci., N. S., Vol. XXIII., 1883. 
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