Explanation of Plate 4. 



Fig. i. Portion of the edge of the pygidium of Fiorinia fioriniae showing 

 the median " notch " formed by the median lobes. 



Fig. 2. Pygidium of salicis, the type of the genus Chionaspis. 



Fig. 3. Portion of the edge of the pygidium of Parlatoria sp. The draw- 

 ing is designed to show the type of " plates " found in the genus 

 Parlatoria. 



Fig. 4. Same from a species of Aspitfiotus. 



Fig. 5. Diagramatic representation of a pygidium, drawn to explain the 

 form of description used in this paper. A, circumgenital gland- 

 orifices. B, anterior groups of dorsal gland-orifices, c, posterior 

 groups of dorsal gland-orifices. D, anus. E, marginal gland- 

 orifices. F, spines of the dorsal surface. G, spines of the ventral 

 surface. H, gland-spines, j, marginal gland-prominence. K, 

 median lobes. L, second lobe. M, third lobe. N, genital orifice. 



