1911.] NATURAL SCIENCES OF PHILADELPHIA. 257 



Peristomium not longer than prostomium, continuing its regular 

 outline and widening posteriorly; deeply cleft below for mouth and 

 bearing the wide, bilobed, hammer-shaped, posterior lip. Nuchal 

 tentacles arising from its extreme anterior border, separated by 

 slightly more than their length and reaching extreme anterior endo- 

 prostomium. Anterior region of body slender and terete, the segments 

 about as long as wide and not much wider anteriorly than posteriorly. 

 Beyond V the segments become gradually shorter, wider and more 

 depressed until in the middle region they are very regularly about 

 eight times as wide as long. Farther back they become gradually 

 narrower and less depressed without change in length till near the 

 pygidium. Pygidium short, cylindroid, abruptly truncated, bearing 

 two pairs of slender divergent cirri, of which the dorsal is twice the 

 length of the ventral and one-half the body width. 



Parapodia (PI. XV, figs. 24, 25, and PI. XVI, fig. 35) exhibit the 

 usual characteristics of the genus. The first five are widely separated 

 and modified, but gradually become less so from before backward. 

 The three cirriform processes (figs. 24 and 25) are present and moder- 

 ately slender and elongated, the notocirrus the longest of the three 

 and reaching the middle of the preceding foot in each case, the neuro- 

 cirrus and the middle cirrus or postsetal lobe each from one-half to 

 two-thirds as long on the different parapodia, the latter the stouter 

 and flattened at the base. Just before and after the gills appear, the 

 notocirrus exhibits a conspicuous constriction and distortion near the 

 base. After the fifth parapodium the neurocirrus becomes rapidly 

 reduced to an opake glandular ridge below the base of the parapodium 

 which for a few segments bears at its lateral end a short blunt papilla 

 which recedes into the ridge in the course of three or four segments. 

 The postsetal lobe becomes reduced rapidly and completely ; beginning 

 with the sixth foot, it becomes shorter and blunt and continues to be 

 changed until at the eleventh it becomes a small, blunt, rounded 

 papilla lying ventral to the setae and almost replacing the here obsolete 

 neurocirrus, but postacicular instead of preacicular. Farther back 

 (fig. 35) it totally disappears. The notocirrus remains well-developed 

 for the entire length, but undergoes gradual reduction in size after the 

 appearance of the branchia?, appearing upon the largest of these as a 

 much smaller lateral process. The neuropodium becomes rapidly 

 shorter and simplified as in other species. 



Branchia? (PI. XVI, fig. 35) simple throughout, the first appearing 

 in connection with the fourth foot (V) or more rarely with the third 

 on IV, in the latter case being usually quite small. They appear as 



