DAVIS : FOSSIL FISH EEMAINS. 
61 
Before leaving the consideration of the relations of the 
Petalodont family to other groups of fossil or living fishes, it may 
be worth while to note the somewhat peculiar resemblance possess- 
ed by some members of the genus Sargus, at present existing in 
the warmer sub-tropical seas. Taking as an example Sargus 
Rondeletti^ Guv. and Yal., the teeth present an extremely inter 
esting arrangement. Along the anterior extremity of each ramus 
of the jaw there are four teeth, deeply rooted or implanted in the 
strong bony framework of the jaw ; the portion of the teeth 
forming the root, and extending some distance beyond the surface 
of the jaw, is broad antero-posteriorly and somewhat contracted 
laterally ; nearer the apex, however, the tooth becomes laterally 
expanded, spreading out into a spatulate concavo-con\^ex crown, 
terminating in a thin straight cutting edge, with highly pohshed 
enamel surface and very sharp. The largest teeth are on each 
side the symphysis of the two rami, and occupy the central portion 
of the jaw, those on each side decreasing in size backwards, the 
posterior teeth being less than half the length or breadth of those 
in front but still preserving the same characters. The resemblance 
to the Petalodonts is probably merely an accidental one. They 
differ in the arrangement of the median teeth which are separated 
by the simphysis of the jaw, and do not extend across it as the 
Petalodonts do. Sargus lives in the waters on the coast of 
Madagascar, and its spatulate teeth are admirably adapted for 
seizing molluscs like the limpet which adhere strongly to the rock 
or other substance on which they exist. The resemblance may at 
least indicate a parallel in the food of the two genera. 
Pristodus falcatus, Agassiz, occurs frequently in the upper beds 
of the limestone series of Yorkshire. A single tooth appears to 
have enveloped the whole of the upper or lower jaw to which it 
was attached, and extended along the palate and floor of the 
mouth inwards, so that the two teeth fit each other. The exter- 
nal edge envelopes the jaws, that of the upper jaw being extended 
downwards so as to considerably overlap the lower one. The 
