Zool.— Vol. i.] MONTGOMERY— GOKDIACEA. 335 



Comparison. — The only other Gordiacea with longitudi- 

 nally arranged elongate areoles are G. rafhaelis, alfredi, 

 and latastei of Camerano, and G. abbreviatus Villot; but 

 all of these differ from G. longareolatus in having the 

 areoles longitudinally grooved. 



2. Gordius aquaticus Linn. 



Coll. Cal. Acad. Sci.: 2 S <5 , City of Mexico ; 2 S S , Berkeley, Cal., winter 

 of 1 89 1. Coll. Univ. of Cal.: S , Berkeley, Cal., January, 1895. 



These are the only specimens as yet seen by me of the 

 true aquaticus from North America ; in all of them the white 

 spots (figs. 13, 14) are clearly marked on the surface of 

 the cuticle and may be seen with a low-power hand lens. 



3. Gordius aquaticus robustus (Leidy.) 



Coll. Cal. Acad. Sci. : $, San Francisco, Cal. ; ?, Berkeley, Cal. Coll. Univ. 

 Cal.: ?, Berkeley, Cal., January, 1895. 



The largest specimen measured 590 mm. 



This is the form, corresponding to G. robustus Leidy, 

 which has been regarded by me (1. c.) as a mere variety 

 of the preceding, from which it differs merely in the absence 

 of the white cuticular spots. In >the true European aquati- 

 cus the white spots are present in most individuals, accord- 

 ing to the description of Romer 1 ; while in specimens of 

 robustus from the eastern United States (from Kansas east- 

 ward) I have never found these spots, though I have studied 

 one or two hundred specimens. Westward of California 

 occurs the true aquaticus, eastward the aquaticus robustus, 

 while in California the two appear to overlap. If white- 

 spotted specimens be subsequently found in any number 

 from the eastern United States, then aquaticus robustus can 

 no longer be retained as a separate subspecies; but with 

 the facts at hand we are justified in assigning it that 

 position. 



1 Eeitrag zur Systematik der Gordiiden Abh. Seckenberg. Ges., Bd. XXIII, 1896. 



