182 IOWA ACADEMY OF SCIENCES. 



PLATE II. 



Fig. 2. Enlarged view of the outside of the right valve and ihe inside of 



the left valve of a shell. 

 Fig. 3. View of the animal with the right valve of the shell removed, and 



most of the right mantle lobe cut away. 

 Fig. 4, Oblique cross-section of an animal through the intestinal coil and 



the pedal ganglia. Seen from behind. 

 Fig. 5. Section through the heart in the same series as preceding. 



I PLATE III. 



Fig. 6. Cross-section of a piece of gill seen obliquely from the side so as 

 to show both the section and the outer surface of a lamella. 

 ' Fig. 7. Diagram of the outer, left, side of the left organ of Bojanus. 

 Fig. 8. Section across an ovarian follicle. 

 Fig. 9. Epithelial lining of the distal portion of the stomach. 

 Fig. 10. Liver follicle showing charged and discharged cells. 

 Fig. 11. Epithelial cells of the organ of Bojanus. 



A STUDY OF THE GENUS CLASTOPTERA. 



ELMER D. BALL. 



In the development of the hind tibiae and the structure and 

 venation of the wings, the insects under consideration repre- 

 sent the highest and most specialized forms of the Cercopidse 

 if not of the Homoptera; marking, as Uhler suggests, an 

 important advance toward the Heteroptera in the increased 

 freedom of the anterior coxae and the possession of a terminal 

 membrane to the corium. 



In order to correctly establish generic characters it will be 

 necessary, first, to separate off those of family value. 



^ FAMILY CERCOPID.E. 



The representatives of the family in this country, at least, 



agree in possessing the following characters: 



Front inflated, convex or compresso produced; antennae inserted in 

 front of and between the eyes; ocelli, two, situated on the disc of the ver- 

 tex; thorax large, sexangular or trapeicoidal; hemelytra coriaceous; pos- 

 terior coxte and femurs short, tibiie spatulate, armed with two spurs, the 

 first once, the second twice as long as tibi;y are wide; tibite and two first 

 joints of tarsi terminated with crescent-shaped rows of spines, third joint 

 with a bifid claw. 



The following genera are represented in the United States: 



Monecphorap Lepyronia,^ AphroiJlwrap Philaenus and*^ Clastoptera. 



These may be easily separated by the character of the venation 



of either pair of wings by reference to plate XII. 



