PLOTOHELMIS ALATA. 145 



little smaller than the dorsal tentacular cirri of the following two pairs ; they are 

 similar in form and have distinct cirrophores narrower than the cirri immediately 

 distad of them. The ventral tentacular cirri of the second somite are very small 

 and are conical in form. The ventral cii-ri of the third somite are similarly much 

 reduced, but they are thin and foliaceous, more like a typical neurocirrus, excepting 

 for minute size. (Plate 23, fig. 5). 



A normal pair of parapodia are borne on the fourth somite, the cirri being 

 large and foUaceous, though the neuropodium is rather small. In a typical 

 parapodium, as from near the thirty fifth somite of the body, the neuropodium 

 is long and cylinchical, distally pointed, and di'awn out into a finely pointed 

 process through which the aciculum extends. The notocirrus arises from a 

 prominent cirrophore attached at the very base of the parapodium. It is 

 normally elliptic or oblong-elliptic, and distaUy somewhat more pointed. The 

 neurocirrus is attached on the ventral surface but httle farther distad than 

 the notocirrus. It is similarly shaped but smaller. Both cirri extend beyond the 

 distal end of the neuropodium, the notocirrus surpassing it by a considerable 

 distance. Forward from this region the no tocirri- become broader and broader, 

 at first becoming more broadly elUptical acute, then broadly ovate and distally 

 more rounded, and finally on the most anterior ones nearly circular in general 

 outline. The neurocirri similarly become much broader in the anterior region. 

 Caudad the cirri change less, but trend more toward a sublanceolate form. (Plate 

 23, fig. 6-10; Plate 24, fig. 1-3). 



The anterior neuropodia bear each a series of stouter simple setae; these 

 are moderately long, a little curved, and are transparent. Caudad they become 

 reduced in number, finally only one, in a ventral position, being as a rule present, 

 the capillary composite setae in the meantime having become numerous. The 

 composite capillary setae in a typical parapodiiun are numerous, long, and 

 unusually fine ; they are soft and flexible, being commonly wavy and even curled, 

 like strands of fine silk. The distal piece in each composite seta is at base a 

 little thinner than the adjacent part of the shaft, narrowing distad to a fine 

 point. 



Locality. Between Lower Cahfornia and the Marquesas Islands : Sta. 3, 

 Agassiz serial no. (lat. 26° 18' N., long. 128° 54' W.). Surface. 28 August, 1899. 

 Two specimens. 



This species greatly exceeds capitata (Greeff) in size (56 mm. against 8 mm. 

 given by Greeff for the length of his typical specimen). As judged from Apstein's 

 figure (Ergebn. Atlant. Ocean * * * Plankton-exped., 1900, 2, H. b., pi. 2, fig. 19) 



