ORDER P(ECILOPODA — POLYPHEMUS. 55 



ORDER VI. PCECILOPODA. 



Head confounded with the trunk ; the anterior part of the body in the form of a shield. 

 Mouth beak-shaped, or composed of appendices occupying the place of jaws. Antenna 

 short and simple or obsolete, usually sessile and distinct. Anterior feet terminated by one 

 or more hooks or pincers adapted for walking or prehension ; the posterior for swimming, 

 and composed of, or attached to, branchial plates or processes. 



GENUS POLYPHEMUS. Lamarck. 



No antennas. Shield very large, subcoriaceous, rounded in front, convex above, separated 

 into two parts by a transverse articulation, the posterior part smallest, spinous on the sides, 

 deeply notched behind. Tail long, trigonal, robust and pointed. Eyes two, sessile, dis- 

 tant, compound, semilunar. Haunches of the first six pair of feet spinous, and act as jaws. 

 Feet twenty-two. Marine. 



Obs. This genus is arranged by Lamarck under a section which he terms Branchiopodes 

 geants, in allusion to the gigantic stature of some of the species. M. Edwards, however, has 

 shown that it is not a natural group, and should not be adopted. Latreille has placed it under 

 a family of this order, which he designates under the name of Xyphosures, and this has 

 been erected into an order by M. Edwards under the same name. According to Straus- 

 Durckheim, they are more allied in their organization to Spiders than to Crustaceans. 



Polyphemus occidentals. 



PLATE XI. FIG. 50. Pincer of the male, 51. 



(STATE COLLECTION.) 



Limulus cyclops. Fabricius, Syst. Vol.2, p. 488. 



L. polyphemus. Latreille, Genera, Vol. I, p. 11. 



L. id. Bosc, Crust, Vol. 2, pi. 16, fig. 6. L. albus, Id. Shell of the young. 



Polyphemus occidentalis. Lam. An, sans vert. Ed. prior, Vol 5, p. 147; Ed. Brui. Vol. 2, p. 339. 



Limulus americanus. Leach, Diet. So. Nat. Vol. 14, p. 537. 



L. sowerbei. Id. Zool. Mis. Vol. 2, p. 72, pi. 34, young. 



Arana cam/echo. Parra, Descripcion, pi. 56. 



Limulus polyphemus. Say, Jour. Acad. Nat. Sc. Vol. 1, p. 435. 



L. id. Dekay, Annals of Lyceum Nat. Hist. Vol. 1, p. 181. 



Description. Body large, particularly of the females. The anterior portion of the shield 

 largest, rounded in front, with a narrow elevated rim ; reflected beneath, and there forming 



