TETRERES NESIOTES. 491 



Each opercular lobe viewed from in front and above is narrowly elliptic 

 in outline, with the dorsal end the narrower. It bears two rows of palcac, an 

 inner one composed of stouter elements, and an outer of smaller, paler ones. 

 The inner paleae on each side in the type number near fifteen, the outer ones 

 thirty-two. Caudad of the outer edge of the operculum on each side is a row 

 of from twelve to fifteen slenderly conical papillae, all subequal in length. They 

 have purphsh spots like the branchiae. Contiguous with the most dorsal 

 stouter papilla on its mesal side is a stout, dark hook crossing the correspond- 

 ing one of the opposite side and sheathed proximally in a papilla. (Plate 75, 

 fig, 7). Just in front of the nuchal hooks in the depression between the two 

 opercular lobes is a long unpaired cirrus with a dark tip. 



The branchial plates are set very obliquely on the ventral surface of each 

 lobe and lie parallel with each other throughout, the lobes being straight and 

 not curved mesad at distal ends. The plates are low, thin ridges, the distal 

 margins of which are gently convex and bear the filaments. In a paratype in 

 which the branchiae are particularly well exposed for study, there are on each 

 side eleven plates. Of these the posterior ones each bear ten filaments. The 

 anterior plates bear fewer. The filaments are long, slender, and thread-like, 

 when fully extended reaching across the peristomium. They have the purplish 

 tinge of the adjacent parts, the pigment conomonly occurring in streaks and small 

 spots. 



Bordering the mouth-fold caudally is a conspicuous, longitudinally wrinkled, 

 transverse ridge which, at each end on each side of the mouth, is raised into a 

 stout, subcylindric but more or less flattened process. Adjoining this on the 

 ectal side is a much longer, stout cirrus and at the ectal base of this, in turn, a 

 setigerous tubercle. The process adjacent to the mouth on each side is typically 

 transversely wrinkled and bears an abruptly narrower, small, distal lobe. 



The second somite is short and distinctly separated throughout. On each 

 side it bears four cirri. These are thick at the base, above which they are ab- 

 ruptly narrowed and are distad slenderly acuminate. They are subequal in 

 length and are much longer than the somite. The most dorsal of these is in 

 line with the dorsal cirri or branchiae of succeeding somites and has an identical 

 structure; the most ventral one is below the setigerous neuropodial tubercle. 



The succeeding four thoracic — or parathoracic — somites are longer. 

 On each of these there is a prominent neuropodial tubercle from the ventral 

 edge of which project a series of paddle-shaped setae, or paleae, much stouter 

 than those of the preceding somites. Above this is a prominent, vertically 



