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 Cum a 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. Morris, in his invaluable work, “A Catalogue of British Fossils,” has arranged the Eurypteridas 
including Eurypterus and Pterygotus, as a family following Limulidai, under the same order. 
[ Paleontology III.] . 50 
