NO. 1368. 



DESCRIPTIONS OF AL'OILIDJJ—WILSOX. 



041 



and situated not at the very margin, but a little way back on the 

 ventral surface. 



The first free sog-nient of the thorax (rig. 17) is about half the width 

 of th(; carapace, while the succeeding- segments diminish rapidl3' in 

 size. The abdomen is about the same width as the last thorax segment, 

 is well rounded at the sides, and terminates posteriorly in a pair of anal 

 papillie which are large, almost spherical in shape, and tipped with three 

 long, sharp spines. 



The first antennse (fig. IS) are three jointed, as in other species, Vmt 

 the basal joint is relativel}^ nuu-h smaller; in fact, it is but a tritie larger 

 than the two spherical 

 terminal joints, but is 

 armed with the usual stout 

 sickle-shaped hook. The 

 bristles and spines on 

 these terminal joints are 

 rather more numerous 

 than in other species. 



The second antenna? are 

 modified into locomotor organs, and ])oth in the segments and in the 

 number and arrangement of the long plumose rowing sette they are 

 exactly like those of follaceuH and catostornl nauplii. The temporar}' 

 mandibular palps are also like those of the species just named, but are 

 attached somewhat farther forward relative to the other mouth parts. 



Fig. 18. — First antenna ok the kewly uai 



«. ARGUI.rs AMERICANVS. 



■II KD I.ARVA OF 



Fig. 19.— .\NTF.RI0R MAXII.I.IPF.n of the newly hatched ARrJULI'S AMERICANrS. 



The anterior maxillipeds (fig. li») are stout, four jointed, and tenni- 

 nate in the usual pair of sickle-shaped hooks, the ventral one of which 

 is barbed. The basal joint of these appendages is very stout, and in 

 its interior can ])e seen the group of large cells Avhich are to form the 

 sucking disks in later development. 



The posterior maxillipeds (fig. 20) are much smaller, five jointed, 

 and very rough on their ventral surface, while the outer biuder of 

 every joint is arnjed with one and often two or more sharp spines. 



These appendages terminate in two small but stout claws capable of 

 independent motion and a conical papilla tipped with two short spines. 

 The ])asal joint has no spine upon its posterior border. 



