KINSHIPS OF SHARKS 97 
survived among the widely evolved genera and families of 
Palzeozoic times. 
_ §. The more primitive types of modern sharks, Chlamy- 
doselache, Notidanus, represent in an almost differentiated 
condition the Palaeozoic phylum. . 
6. The modern rays are derived in early Mesozoic times 
__ from the main shark stem, not (in the opinion of the 
_ writer) descended from Cestracionts, Pristids, Pristiopho- 
rids, or even (?) Rhinids. | 
_ 7. Chimezeroids, next to be discussed, represent the most 
ancient of known offshoots from the (Pre-Silurian ?) sharks : 
they are not degenerate in their essential structures, nor 
are they connected with the ancestral phylum of the lung- 
fishes, save through a common descent from early shark- 
like ancestors. 
These results the writer has expressed in the diagram 
on the following page. The diverging phyla are indicated 
as they are represented historically ; their primitive con- 
currence with the main line of descent is suggested by 
dotted lines. 
H 
