ONUPHIS PROALOPUS. 269 



and the distal edge is straight and runs obliquely from one tooth to the other. 

 (Plate 40, fig. 8). The pectinate setae are transparent and delicate; the stalks 

 are usually very long, variable in length; the expanded distal piece is large, in 

 outline somewhat cuneate but asymmetrical, one side being oblique and pro- 

 longed, the edge of the other diverging but little from the axial line; the distal 

 edge is a little oblique, its teeth nearly uniform in length. (Plate 41, fig. 2). 

 The setae of the dorsal group are comparatively short and slender; each is 

 slenderly tapered to a fine tip, more or less bent near middle of exposed portion, 

 and is narrowly limbate. The ordinary ventral setae are coarse, a Uttle bent or 

 curved and drawn out distally to a fine point; they are narrowly bilimbate. 

 (Plate 40, fig. 7). 



The maxillae are thin and translucent, irregularly blackish on part of the 

 edges. Each carrier-plate of maxillae I is at the anterior end incurved, the 

 remaining greater portion of the plate being semicircular, with the convexity 

 ectad, but the plate as a whole narrower than long, narrowly acutely incised at 

 the middle line posteriorly, the edges dark, the dark area more extensive on each 

 side of the caudal incision. The blades are slenderly and evenly tapered distad, 

 the distal end strongly curved mesad. The outer left plate of maxillae II has 

 eight teeth, the inner one nine somewhat smaller ones, and the right plate ten 

 teeth which are acute and retrorse and decrease in length gradually and regu- 

 larly proximad. The right maxilla III is a long plate paralleling II proximally, 

 where it is smooth and edentate, but strongly curved ectad anteriorly and on 

 the curved portion bearing a series of ten erect straight teeth; the left maxilla II 

 is a shorter, less curved piece bearing only seven teeth. Each maxilla IV bears a 

 single tooth. (Plate 40, fig. 4). The mandibles are small and weakly developed, 

 only slightly chitinized. The masticatory plates are small and transparent, 

 with the edges smooth. 



The single tube in the collection is incomplete. The part present is 75 mm. 

 long and has a maximum diameter of 5.25 mm. It consists of the usual thin 

 lining membrane covered with a uniform layer of fine mud. 



Locality. Off Peru: Sta. 4653 (lat. 5° 47' S., long. 81°24' W.). Depth 

 536 fms. Bottom of dark brown volcanic mud. Bottom temp. 41.3° F. 12 

 November, 1904. One specimen in its tube. 



This species is hke mannognathus, sp. nov., and vexillaria Moore in the 

 weak development of the mandibles and in other general structural characters. 

 It may readily be distinguished by the very long first parapodia and in having 

 the branchiae first appear on the sixth parapodia, as well as by other details 

 throughout. It is a much more slender species. 



