160 J. D. Dana on Zoophytes. 
leozoie fossils to themselves, they submitted the examination of 
the Jurassic and cretaceous to M. d’Orbigny ; the comparative anat- 
omy of the fishes to M. Agassiz; those of the plants to MM. Ad. 
Brongniart and Morris. M. de Verneuil likewise cited as con- 
tributor to this work, M. Owen, to whom they were indebted for 
interesting observations on the structure of the teeth of the genus 
Dendrodus, and on the characters of certain mammifers; Lieut. 
M. Kokcharof, who accompanied the expedition, and who con- 
structed a table of the minerals of the Ural, inserted at the end 
of the first volume; and, lastly, M. Viconte d’Archiac, of whose 
advice they frequently availed themselves in the course of the 
publication. In conclusion, M. de Verneuil congratulates him- 
self in thus finding an opportunity to express to these gentlemen 
the obligations of the authors. 
Arr. XVI.—On Zoiphytes, No. IV; by James D. Dana. 
GerocraPHicaL DistrisuTion or ZoopHyTes.* 
Heat, light, pressure, and means of subsistence, influence 
more or less the distribution of all animals; and to these causes 
should be added, for water species, the nature or condition of the 
water, whether fresh or marine, pure or impure, still or agitated, 
Next to the character of the water, heat is the most prominent 
limiting agent for marine animals, especially as regards latitudi- 
nal extent, while light and hydraulic pressure have much influ- 
ence in determining their limits in depth. 
Although these causes fix bounds to species and families, they 
do not necessarily confine tribes of species to as small limits. 
This is sometimes the case, and it is nearly true of a large group 
of zoophytes; yet other tribes and orders include species whose 
united range comprises all the zones, from the equator to the po- 
lar ices, and every depth, to the lowest which man has explored 
affording traces of life. 
Order Hydroidea.—The Hydroidea are met with in all seas 
and at great depths, as well as at the surface. The tropics, and 
place of the faded coral blossom. 
prs aa ee 
* Report on Zoophytes, p. 101. 
