3 8 CRUSTACEA OF ALABAMA. 



genus Crepidocercus and the species Pleuroxus denticulatus and P. hamatus, P. affinis, 

 P. unidens, P. procurvus, all are found abundant southward, thus adding evidence to that 

 already adduced to prove that the United States is largely indebted to South America 

 for what is peculiar to its fauna. 



ORDER PHYLLOPODA. 



Though obviously very closely connected with the Cladocera, the living members of 

 this order form a rather homogeneous group in spite of great diversity of form. Great 

 difference of opinion exists as to the origin of the group, some claiming for it a high 

 antiquity, while others, like Packard, consider it a recent off-shoot of the Cladocera. 

 The great number of similar segments found in the body of most Phyllopods may be 

 taken, indeed, as a sign of inferiority, but it is doubtles inferiority due to degradation 

 rather than the persistence of a primitive condition. 



The appendages are two pairs of antennae, jaws, two pairs of maxillae and often a 

 largfe number of foliaceous feet from which the order receives its name. Two well- 

 marked sections are distinguishable, in one of which the whole or much of the body is 

 encased in a bivalved shell, in the other the body is free and elongated as in Copepoda. 



The species of this order are not only among the most beautiful of Crustacea but 

 are especially important in the light of their physiological peculiarities. In this group 

 the variability of the form of the body under changing physical conditions has been most 

 aptly illustrated. A change in the saltness of the water being sufficient to produce a 

 change in form adequate to rank as of generic importance. The greater number of spe- 

 cies live in fugitive pools and it seems as though in many cases dessication is prerequi- 

 site to the hatching of the eggs. 



For the most complete account of the group the reader is referred to Dr. Packard's 

 monograph in Hayden's twelfth annual report, while an account of the development is 

 given by the writer, in Vol. I, of the Bulletin of Denison University. 



FAMILY LIMNADIADyE. 



Body covered by a bivalved shell, eyes contiguous, first antennae minute, second 

 antennae biramose. 



Genus Limnetes. 



Limnetes gozddii, Baird. Probably not rare in northern Alabama. 

 Estheria compleximanus, Packard. 



Estheria mexicana, Claus. The existence of these two species is inferred merely 

 from their known range. 



