452 PROCEEDINGS OF THE ACADEMY OF [Juiie, 



which arises from middle of foot, ventral cirrus shorter, arising from base 

 of foot and ending opposite root of dorsal cirrus. 



All other parapodia are much smaller, but the 2d and 3d project 

 slightly forward, and are somewhat transitional in other respects also; 

 dorsal cirri and postsetal lobes increase in length and become slender 

 and tapering, reaching their maxinuuu by XI or XII, when the latter 

 is fully ecpial to the body of the foot, and the former is 3 times as long 

 and capable of reaching the dorsal mid-line, though habitualh' carried 

 outward and backward; beyond this region they decrease in length, 

 the postsetal lobe retaining its slender form, but becoming of insignifi- 

 cant size by the middle of the Ijody, while the dorsal cirriis reaches as 

 far as the tips of the setie. The ventral cirrus diminishes in size rapidly ; 

 on the 2d and 3d it remains as a short thick cirrus, by the 4th it is a 

 low dome-shaped opacpie whitish lobe below, and distinctly separated 

 from, the foot; posterior to XII it (hminishe«, and has practically dis- 

 appeared by XVIII. 



The l)ranchicT are characteristic. They usually begin as a single 

 filament, or occasionally two, on XIII or XIV, arising with the dorsal 

 cirrus from a common base, and dorsad of the latter; this ciuickly 

 becomes subdivided c|uite to the base, which shifts its position to the 

 caudal side of the cirrus. The flivision into 2, 3 and 4 filaments takes 

 place somewhat irregularly, but each filament attains practically 

 its full length immediately; by XVIII or XX the typical number of 5 

 is reached, and continues, with occasional variations to 6, to about 

 XXXV, when 4 again becomes the predominant number to about 

 XLVIII, beyond Avhich it further diminishes; somites LVI to LVIII 

 bear only small but distinct branchial tubercles, and LIX, the last 

 segment bearing parapodia, has none. Some variation in the number 

 of filaments occurring on somites toward the ends of the series is notice- 

 able. The filaments of which the branchis are composed are very 

 dehcate and, as their wrinkled condition indicates, very contractile; 

 they are generally about f as long as the dorsal cirri, but probably 

 ecjual or exceed these in life, are deeply cleft and arise in a cluster, 

 though occasionally a more pectinate arrangement is indicated. 



Setae of four kinds, two being coarse uncini. Compound uncini 

 confined to the first 4 parapodia, yellow, stout; appendix curved, bifid, 

 the terminal process large and hooked, the accessory one much smaller, 

 both included in the delicate double truncated guard. This is the only 

 form of seta in the first foot, in which some of them l:)ecome very large 

 and, in one example, lose the articulation, though this is present in 

 the type specimen; they become successively smaller on the 2d, 3d 



