52 THE ANNELIDA POLYCHAETA. 



to the Chilean coast. In general structure they agree with adults of hirsuta 

 from San Pedro excepting that the notopodial setae are comparatively more 

 slender, being mostly clearly more slender than the neuropodials and more 

 numerous than is typical, and that the anterior eyes are rather more dorsal in 

 position and thus clearly visible in dorsal view. Above they show the char- 

 acteristic nuchal process from the anterior edge of the first metastomial somite 

 which, as pointed out by Ehlers, serves as an easy distinguishing mark in com- 

 parison with the closely related Harmothoe polytricha (Schmarda) which occurs 

 on the other side of the isthmus in the Caribbean region. The parapodia of the 

 peristomial somite bear three (or sometimes two) conspicuous setae. The small 

 specimens from Panama are described in full below. 



The body is short. It is widest near the junction of the first and second 

 fourths of the length but narrows only weakly from there caudad to the begin- 

 ning of the last fourth over which it narrows more strongly to the pointed anal 

 end; anteriorly also narrows strongly to the prostomium. The dorsum is only 

 sUghtly arched. Venter also slightly arched, and presenting a sharply limited, 

 caudally tapering, ridge. Total length of one specimen near 11 mm.; greatest 

 width, exclusive of parapodia, 2 mm.; width to ends of parapodia, 3.5 mm.; 

 width to ends of setae, 5.6 mm. Number of somites thirty-seven. 



Prostomium decidedly wider than long, sloping strongly from behind 

 forwards. A wide median longitudinal furrow dividing it into two symmetrical 

 halves. Each half rises to a longitudinal ridge extending forwards to the apex 

 of the peak, the prostomium otherwise smoothly rounded. On each side it 

 bulges convexly into an optical lobe. Each anterior eye situated rather laterally 

 on the lobe and distinctly visible from above. The posterior eyes are much 

 closer together and are dorsal in position; they are more than three fourths 

 the diameter of the anterior ones, from which they are separated by three times 

 their diameter or nearly so. The peaks are conspicuous; each is a stout sub- 

 conical process extending over the base of the corresponding lateral tentacle, 

 its abruptly narrower tip separated by a wide space from the median ceratophore, 

 though this space is less than the half-diameter of the ceratophore at its base. 

 The peaks in one specimen are darkened. The ceratophore of the median tenta- 

 cle is stout and much narrowed distad; it is blackish in color, contrasting strongly 

 with the prostomium; the style is missing. The lateral tentacles arise from 

 beneath the base of the median ceratophore. Each lateral ceratophore is 

 cylindrical, shorter and much less thick than the median. In one specimen the 

 style is nearly twice the length of the prostomium and in the other specimens is 



