WATERLIME GROUP. 393 



" pterus, at least for the very closely allied genus Eurypterus, have been 

 " sought by different naturalists among the Poecilopoda, the Phyllopoda 

 " ( particularly Apus), and the Copepoda ; and Milne-Edwards has sug- 

 " gested that Eurypterus possibly holds an intermediate position between 

 " the Copepoda and the Isopoda". 



I am not prepared to agree with Mr. Huxley in the opinion (expressed 

 in the succeeding page of the paper cited ) that this form and Pterygotus 

 (Himantopterus) are related to Cwna and Mysis ; though in every step of 

 the comparison, the larval expression of the fossil, so to speak, is con- 

 stantly forced upon our notice. 



Mr. Dana, from an examination of some of the drawings of my speci- 

 mens, suggested an analogy with Sapphirina ; and this analogy with the 

 allied genus Pterygotus is certainly in many respects very conspicuous, 

 particularly in the form of the animal, and in the situation of the cornea 

 lenses on the margin of the carapace. 



As my examinations have progressed, and the parts now shown have 

 gradually been brought out in their true relations by the study of a large 

 number of specimens, many structural analogies with Limulus have been 

 observed. At the same time, both in the form of the feet and in the 

 jointed body, the great dissimilarity with Limulus is apparent ; but I am 

 not prepared to maintain that these external differences are of ordinal 

 importance*. 



The original description of Dr. Dekay recognized four pairs of feet, the 

 third pair of which were longer than the two anterior pairs and the 

 fourth pair, which are placed near the junction of the head with the 

 abdomen ; being, as he says, larger in proportion to the body than in any 

 living genus of Crustacea with which we are acquainted.  



The description and figure of Dr. Harlan has added nothing to our 

 knowledge of these organs, and I have not seen any illustrations which 

 better serve to represent them. Mr. Salter remarks that "All these re- 

 " presentations showed that the Eurypterus possessed at least three pairs 



* Mr. MoBRis, in hit invaluable work, "ACatalogne of British Fossils," has arranged the Eurypteridaa 

 including Eurypttrun and Pterygotus, as a fuiuily I'uilowing Limulidte, under the same order. 

 [ PALiEONTOLOOY III.] 50 



