NEREIS LEUCA. 205 



shafts ending in unsymmetrical, or heterogomphous, sockets. The blade in 

 these heterogomphs is short. It ends in a slender, short, distally narrowly 

 rounded end region which is not dentate, proximad of which along one margin 

 it is densely fringed. (Plate 32, fig. 4, 5). 



The proboscis is but little extruded, making a detailed account of the 

 number and arrangement of the paragnatha impracticable. Of the areas of 

 the oral ring, V and VI are wholly unarmed ; VII bears small, nodular paragnatha 

 irregularly transversely arranged across its extreme distal end; each area VIII 

 lacks paragnatha excepting a few in the portion contiguous with VII, from the 

 group on which they are not separated and might be regarded as belonging with 

 them rather than on VIII. All maxillary areas seem to bear a few paragnatha. 

 These are longer and more conical than those of the proximal ring. They are 

 few in number and isolated from each other. 



Locality. Off Isthmus of Panama, 72 m. S. W. of Mariato Point: Sta. 

 4631 (lat. 6° 26' N., long. 84° 49' W.). Depth 774 fms. Bottom of green sand. 

 Bottom temp. 38° F. 3 November, 1904. One specimen. 



Aside from the distinctive nature of the arrangement of the paragnatha, 

 a characteristic feature of this species is the uniformity in character of the para- 

 podia, with the much enlarged proximal or cirrophorous region of the notocirrus 

 and the much inflated dorsal lobe in front of it. In side view these enlargements 

 in their relation to the cutus appear much like those of some species of the 

 Alitta (Thoosa) group of Klnberg, excepting that they are not foliaceous. The 

 non-pigmented condition of the ocular areas may be a normal and degenerate 

 state in the species. 



Nereis leuca, sp. nov.' 



Plate 32, fig. 6-8; Plate 33, fig. 1-6. 



Epitokous Male (Heteronereis). 



Body colorless and transparent throughout, excepting the eyes, which are 

 black as usual, though the posterior division of the body appears somewhat 

 darkened from its contents. 



Total length 16 mm. Greatest width, exclusive of parapodia, 1.5 mm. 

 The nereid and heteronereid divisions are sharply distinguished as usual, the 

 heteronereid division the longer. The nereid division consists of seventeen 



' XeuKos, colorless. 



