NEREIS SEGREX. 203 



the side of the prostomium, the surface of attachment extending from base of 

 the prostomium to within a short distance of its distal end. The basal article 

 is weakly conically narrowed toward its end, where it is truncate. The distal 

 article is abruptly much narrower and is subcylindric and short. The median 

 anterior extension of the prostomium is a little constricted or grooved a short 

 distance proximad of its distal margin. The tentacles, though not contiguous, 

 are attached close together and project directly cephalad. They are subulate 

 and wholly smooth. 



The peristomium above is somewhat more than two thirds the length of 

 the prostomium and one and a third times as long as the second somite. It is 

 narrowest across its caudal end. The lower half of the somite, from the middle 

 of each side across to that of the other, forms a thickened lower lip which is 

 crossed longitudinally by numerous deep sulci. The dorsal part of the ring 

 is smooth, or nearly so. On each side a somewhat semicircular lobe from a 

 deeper level projects cephalad against the base of the palpus and bears the 

 tentacular cirri. Each tentacular cirrus has a very short, relatively thick cirro- 

 phore, the style being slender and subulate and wholly smooth. All of the 

 tentacular cirri are short. Each anterior ventral cirrus is attached at the 

 anterior margin of the cirriferous lobe, and when laid back reaches only upon 

 the peristomium itself or barely to the anterior border of the second somite. 

 It projects normally ectoventrocephalad. The anterior dorsal cirrus is attached 

 immediately dorsad of the ventral, their cirrophores being contiguous at base, 

 and projects a little ectad of dorsad. When laid back along the body, it reaches 

 to the third somite. The posterior dorsal, which is attached just dorsad of the 

 ventral, has a cirrophore longer than that of the others and reaches back upon the 

 fourth somite. 



The metastomial somites are all essentially undivided, though in the middle 

 region of the body they may show a shallow and rather wide transverse furrow 

 that curves caudad at the ends in crescentic manner and separates off a caudal, 

 more elevated, region. On each side above the base of the parapodium, the 

 somite is elevated in a glandular area not present on the most anterior somites 

 and in the more caudal ones becoming more elongate and narrow. The somites 

 are strongly arched above and are flattened ventrally, where they show a distinct 

 and rather deep neural furrow excepting on the first few. The somites increase 

 in length caudad to the sixth, when they decrease and quickly attain a length 

 that is uniform over the remaining part of the type. 



A typical parapodium is strongly flattened in the direction of the long axis 



