ONUPHIS PACHYTMEMA. 283 



upper surface being slightly concave. The membranous guards rise broadly 

 a little above the teeth. (Plate 49, fig. 8). On the first three parapodia there 

 are elongate jointed crochets, the articulation being far distad, and the second 

 article short; distally the second article is bidentate, the subapical tooth small; 

 the guards extend much above the level of the teeth and are narrowed gradually 

 to a slender acute point distally. (Plate 50, fig. 1). These are replaced on the 

 fourth parapodia, etc., by coarse setae which are drawn out distally to a fine 

 point and may or may not show an imperfect jointing. (Plate 50, fig. 2). The 

 ordinary ventral setae are finely pointed, distally curved, and narrowly shortly 

 limbate on the convex side. (Plate 50, fig. 3). 



The acicula are of the typical form, each narrowing strongly at the distal 

 end, and the protruding portion fine, subcapillary, and curved. (Plate 50, fig. 6). 



The maxillae are rather thin, light brown in color, with black edging. Max- 

 illae I have the plate formed by the carriers narrowed across the anterior end, 

 below which it bulges convexly on each side to narrow again caudally; there is 

 an open V-shaped median incision from the caudal margin; an inverted, tri- 

 angular anterior area on each half is thicker, as usual. The blade of each maxilla 

 is proximally very broad, being abruptly much narrowed distad of the middle 

 in a characteristic way. (Plate 49, fig. G). Maxillae II have the left paired piece 

 bearing ten teeth; the unpaired plate has also ten teeth, with a smooth proximal 

 edge longer than that of the paired plate. The right maxilla II has the distal 

 process narrower and tooth-like, being curved mesad like the other teeth with 

 proximad of it ten teeth, making the full number of teeth eleven. (Plate 49, fig. 6) . 

 The number of teeth on maxillae III was not ascertained. The masticatory 

 plates of the mandibles are large and obliquely elongate, with the distal angle 

 subacute. The anterior edges of the plates meet mesally at an angle of less than 

 ninety degrees ; they are straight and smooth except for a single acute incision 

 at about the middle of the length of each. There is a short incision on the outer 

 end in the usual position. Especially on the caudal half of each plate striae 

 parallel to the caudal margin are pronounced. The two plates are broadly in 

 contact mesally. The stems taper and diverge caudad; they show striation 

 rather distinctly. (Plate 49, fig. 7). 



Of the several tubes the longest measures near 460 mm., with a maximum 

 diameter of 5 mm. The inner tube or lining consists of a tough, whitish, trans- 

 lucent membrane over which is the layer of fine, closely adhering mud, which 

 is dark greenish grey in color. 



Locality. Off Peru: vicinity of Sechura Bay. Sta. 4658 (lat. 8° 30' S. 



