1881.] | Loology. 1003 
teristic structures of the adult. Thus in the Ao//usca the vessels 
of the circulatory system are diverticula of the general body-cavity 
with which they freely communicate. n the other hand the 
circulating vessels of the Axterocela never communicate with 
the body-cavity, but originate from the digestive system, or inde- 
pendently. In the Psexdocelia the nervous system is derived from 
the mesenchym, except perhaps the supracesophageal ganglia 
of Mollusca. In the Azterocela, on the other hand, the central 
system is developed from the epiblast, and the peripheral system 
from the epiblast and external layer of the mesoblast. 
THE Tortotses oF Tucson.—There are two land tortoises and 
a fresh-water turtle found here that are not given in the list of 
reptiles for Southern California, by Dunn and Fisher, published 
in the April number of AMERICAN NATURALIST. 
One of the terrestrial tortoises! resembles at first glance the 
common box tortoises, Cistudo virginiana, but differs in the orna- 
mentation of the plates on the carapax and on the sternum. The 
whole exoskeleton is marked with brown and yellow stripes and 
spots; brown predominating on the carapax and yellow on the 
sternum 
immediate want of water. 
_--) Cistudo ornata Agass. 
— ® Xerobates agassizi Cooper. 
