506 
PALAEONTOLOGY OF NEW-YORK. 
that this graptolite was composed of four semielliptical parts joined at their straight 
sides, and projecting rectangularly to each other; presenting on each of the four 
margins a series of serratures, which, penetrating towards the centre, \\t»re all united 
in a common canal, and all sustained upon a simple radicle. 
Under this genus have been described the following species from the Canadian 
collection : 
Phyllograptus typus, P. ilicifolius, P. angustifolius, and P. similis. 
While these discoveries have been made in Canada, giving us for the 
first time a correct knowledge of the mode of growth and the varying 
forms of these bodies, I have not neglected opportunities of increasing 
our knowledge of these fossils from localities within my reach. The lo¬ 
cality of graptolites near Albany has heretofore furnished several species, 
which, now that we know better their original forms, olfer additional 
information, and become of greater interest both in their zoological and 
geographical relations. 
At this locality, some specimens have been obtained which show 
apparently the mode of reproduction in this family of animals, which is 
more similar to the hydroid polyps than to the Bryozoa*. 
The specimens in which this feature has been observed, first show a 
slight swelling or vesicle proceeding from the axils of the serratures : 
this vesicle, which in the beginning is barely perceptible beyond the out¬ 
lines of the margin, swells and becomes elongated, the extremity finally 
much inflated, and the base of the footstalk extended and attenuated. As 
this process of development goes on, the sac or inflated portion curves 
downwards, and finally becomes ruptured or dehiscent on the lower side 
near the extremity. At this period, and sometimes previously, the sac, 
which appears to be an extremely thin membrane and almost without 
substance, shows one or two elongated fibres, like the central midrib or 
the marginal longitudinal fibre of the graptolites. At a more advanced 
stage the substance of the sac gradually disappears, apparently by de¬ 
composition, leaving the slender fibre still attached for some time to the 
axil of the serrature. 
* This notice was read at the meeting of the American Association for the Advancement of Science at 
Baltimore in 1858, accompanied also by references to the Canadian graptolites. 
