248 77^1? America/i Geologist. April, looo 
descended from them than from the elasmobranchs along Hnes 
at present uncertain, but of paleozoic date. 
In conclusion Prof. Traquair maintains the connection of 
the Heterostraci and Osteostraci as a natural group whose 
parts are closely and genetically related and that the class 
of ostracoderms "is not a mere delusion, founded on the oc- 
currence together, geologically of their fossil remains." And 
he adds : 
"The fossil fishes from the Silurian rocks of the south of 
Scotland, described in the preceding pages, constitute eight 
species, which are all new to science." "And whether the 
views which I liave expressed regarding the phylogeny or 
classification of these and allied forms be adopted or not these 
recent discoveries by the geological survey have opened out 
a new vista in the field of paleozoic ichthyology." 
We conclude with a single remark on the phylogeny sug- 
gested by Prof. Traquair. It is that so far as the evidence at 
present warrants a deduction the true ostracoderms are older 
than the true elasmobranchs. No elasmobranch yet known 
from the English strata equals in age the so-called Scaphaspis 
(Cyathaspis?) of the English Lower Ludlow. Nor does any 
Onchus, granting the elasmobranch nature of this fossil, ex- 
ceed the Palaeaspis of the Clinton rocks of Pennsylvania 
and both are much later than the apparently petromyzont 
fossils from Canon City, Colorado, described by Walcott. 
The line of descent from a primitive elasmobranch type seems 
therefore, far from certain. Whether the suggestion stands 
or falls, the result will in no way detract from the great value 
and interest of Prof. Traquair's contribution to fossil 
ichthyology. e. w. c. 
