630 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. XXVII. 



Yentral sirrface {f[g. 2). — The frontal lobe is plainly divided into an 

 anterior and posterior portion V)y a line parallel with the edge of the 

 carapace except at either end where it curves around abruptl}" to the 

 base of the anteunre. From the center of this line there projects 

 backward into the posterior portion a triangular area (the post-frontal 

 triangle) whose ventral surface is on the same level as the rest of the 

 carapace. But the remainder of the posterior portion on either side 

 of the triangle is hollowed out for the antenntt^. The ventral surface 

 of the triangle, the anterior rim, and the anterior half of the lateral 



Fig. 



-VEXTRAL view of female ARGIUS AMERICAXl'S. 



areas are thickly covered with sharp triangular spines of considerable 

 size, which must hold the creature ^ery firmly on its host. 



Antennm (fig. 3). — These are small ))ut well armed with stout hooks 

 and spines. 



The proximal portion of the basal joint of the first pair carries two 

 stout spines on its inner ])order, the posterior of which is strongly 

 curved backward. The distal portion of this joint has the usual hooks 

 on the outer and anterior margins and two spines upon its posterior 

 margin, one of which is long and stout, while the other is very slender. 

 The terminal portion of this antenna is two-jointed and projects con- 

 siderably beyond the basal portion. The second antenna are four- 

 jointed, and each carries two large triangular spines on its inner 



