OF THE CARBONIFEROUS XIPHOSUROUS FAUNA. 157 



From the. Crustaceii the Podostoiuata diflfer iu the lack of fuuctioiial autennse and mouth 

 parts ; in the brain iunervatinj? the eyes (compound and simple) alone; in the shape of the head 

 and of the pygidium or abdominal shield, and in the arterial coat enveloping the ventral nervous 

 cord. 



The Podostomata are divided into two orders : 



I. Mefostomata with three suborders, Xiphosura, Synziphosura, and Eurypterida. 



II. Trilobita. 



Explanation of Plate T. 



Fig. 1. CycluK americautis Pack. xf. la, lateral view restored. X^. 



Fig. 2. Dipellis diplodiscus Puck. Natural size; 2a, the same restored. Xf. 



Fig. 3. Prestwichia danw Meels. Natural size ; restored ; dorsal view. 



Fig. 3a. Prealwichia danw Meek. Natural size ; partly restored ; ventral view. 



Fig. 4. Preslwichia longispina Vsti'k. Partly restored. Xf. 



Fig. 5. Belinurus lacoei Pack. Partly restored. x2. 



All the figures on this plato drawn by Dr. J. S. Kingsley, with corrections by the author. 



Explanation of Plate VI. 



Fig. 1. Prestwichia dana; showing the limbs; la, the reverse. 



Fig. 2. Prestwichia danw, showing the interior; 2a, the same, another specimen. 



Fig. 3. Prestwichia longispina, natural size. 



Fig. 4. Cyclus americana, natural size; 4a, reverse of the same. 



From photographs taken by Mr. R. L. P. Mason, Providence, R. I. 



Explanation of Plate VII. 



Fig. 1. Palwocaris typus M. & W., natural size. 



Fig. 2. Palwocaris typus M. & W., natural size. 



Fig. 3. AnthrapaUimwn gracilis M. & W., carapace laterally flattened. 



Fig. 4. AnthrapnUrmnn gracilis M. & W., from a small specimen without tlie carapace. 



Fig. 5. Anthrupala'nion gracilis M. & W., carapace wanting. 



Fig. 6. Anthrapalamon gracilis M. & W., carapace wanting. 



All the figures of natural size and from photographs taken by Mr. F. O. Draper, Pawtucket, R. I. 



