PLATE 80 A. 



Fig. 1 - 6, & 11 - 17. EuRYPTEEtrs uemipes. 404* 



1 . The ventral side of an imperfect specimen preserving the tlioracic segments and four of the 



abdominal joints, with the impression of one of the swimming feet entire, and the other 

 with the penultimate joint separated. Impressions of the maxillai-y plates remain, show- 

 ing their original form, as also the form of the post-oral plate. The bases of the four 

 anterior paii-s of feet still remain, showing the place of their origin. 



The last joint of the foot appears in this individual to slide over the triangular piece 

 of the preceding joint upon the lower side, which is not true : this appearance arises from 

 the fact that it is a mould of the upper or dorsal surface of this organ. 



2. A part of the head of this species, showing part of the three first feet, while the fourth 



is entire. 



3. A dissected swimming foot, showing its attachment to the maxillary plate, the form and 



proportions of the joints, and mode of articulation. 



4. The broad terminal joint of the swimming foot, showing the notch at the extremity and 



the small terminal palette. These separated joints are of not unfrequent occurrence in 

 strata where the Eurypterus is found. 



5. A transverse section of the abdominal portionof one of these fossils : the section is oblique 



to the body, and the appearance indicates that it has suffered little from compression. 



6. A fragment of a crustacean associated with the E. remipes at Waterville, the relations of 



which have not been determined. 



11. A small carapace of E. remipes, with the first thoracic segment. 



12. The lower surface of one side of the cephalic shield. 



13. The post-oral plate of E. remipes. 



14. The same organ of E . robustus. 



15. The anterior portion of the same organ (a fragment) of Dolichopterus macrocheirus . 

 17. The same organ, copied from the specimen figured on Plate lxxxiii a. 



16. The same organ of Pterygotus osborni. 



Fig. 7. Eurypterus MicEorHxnALMUs. 407* 



7. The carapace, natural size, preserving a part of the first joint of the thorax. 



Fig. 8. Pterygotus macropqthalmus. 418* 



8. The carapace, natural size. 



8 a. A small portion enlarged, to show more distinctly the obloug tubercle, and the small 

 eye-like spots which are faintly visible to the naked eye. 



Fig. 9. Pterygotus osborni. 419* 



9. A figure of the specimen, natural size. A reference to the parts of EuaYPTKnus will explain 



the relations of the parts of this figure. 



Fig. 10. Ceratiocaris aculeatus. 422* 



10. The posterior joint of the body and tail-spines. 



