STATE GEOLOGIST. 121 



body; shell covering but a part of the dorsal region. Feet all with 

 an internal dentate, and an external lamellate appendage. Caudal 

 seta upon a long process of the post-abdomen. 



Sp, 1. Polypliemus pediculus, Linn. 



(Plate B^ . Figs. 4—6.) 



Monoeuliis pediculus, linn^us, 1746. gmelin, Linn. Syst Nat. fabricius, Ent. Syst., 



etc. SULZER, Insecten. manuel, Encyclop. Meth. 

 Monoculiis pediculus ramosus, de geer, Mem. pour serv. a I'Hist. des lus. 

 Polyphemus oculus, mceller, Zool. Dan. Prod, et Entomost. ccvier, Tab. element 



LATREiLLE, Hlst. Nat. Cfust., etfi. LEAcn, Edin. Encyc. 

 Poli/p/iemttsstognorum, LEACH, Diet. Se, Nat. latreille. Guv. Rig. An. dema- 



REST, Cons. Gen. Crust. 

 Polyphemus pediculus, straus, Mem. Mus. d'Hist.,etc. m.edwards, Hist. Nat. Crust. 

 Jlf onocuZus poZj/phemus, JURiNE, Hist. Nat. Monoc. 



Cephaloculus stagnorum, lamarck, Hist. An. "Vert, bosc, Man. d'Hist. Nat. Crust. 

 Monoculus oculv^, gmelin, Linn. Syst. Nat. 

 Scalicerus pediculus, koch, Deutsch. Crust. 

 Polyphemus pediculus, baikd, Brit. Entom. 

 Polyphemus oculus, lievik, Branch, d. Danz, 

 Polyphemus stagnorum, fischer, Ueber die in d. Umg. von St. Petersburg, vorlcom. 



Crust. 

 Polyphemus pediculus, ltlljeborg, De Crust, ex ord. trib. 

 Polyphemus oculus, leydig, Naturg. d. Daph. 



Polyphemus pediculus, schoboler, Neue Bsitr. zur Naturg. d. Cladoceren. 

 Polyphemus Tcochii, " " " " 



Polyphemus oculus, '" " " " 



Polyphemus pediculus, v. b. mueller, Danmark's Cladocera. kdkz, Dodelias n euer 

 Cladoceren. weismann, Beitr. zur Naturg. der Daplin olden. 

 bikgb. Notes on Cladocera. 

 Polyphemus oecidentalis,^ herrick. 



There are two well-marked varieties of this species: one is found 

 commonly in the clear lakes; the other, which I have only once 

 seen, was found in a very shallow weedy marsh. The difference in 

 size is quite remarkable. Our ordinary form measures less than 1 

 mm. The larger form, including the stylets, is 1.6 mm. The 

 ordinary variety, although highly colored, is yet transparent, while 

 the large variety is deep red and quite opaque. The relationship 

 between the two forms is quite like that maintaining between 

 Diaptomus stagnalis and D. sanguineus. Some slight structural 

 differences are observable between the two varieties, as in the form 

 of the antennules, yet quite insignificant when compared with the 

 striking difference in size and coloration. Number two may be 

 called 



1 Polyphemus occidentalis,Dekay = Limulus. 



