SONATSA. 415 



an exceedingly fine point the distal region immediately below which, at least 

 in those of most somites, presents series of cilia or pectinae somewhat as in 

 Isocirrus planiceps. (Plate 73, fig. 1, 2). The uncini with exposed portion 

 bent up at neck, the bm-ied portion curved. Exposed part with a distinctly 

 narrowed curved region, or cervix, above a well-marked shoulder. The head of 

 uncini of first segments nearly always with four hooks or teeth, more rarely 

 with but tlu-ee, of which the largest is typically nearly straight, occasionally 

 curved at tip. (Plate 72, fig. 4-6). The uncini on the middle and posterior 

 somites similar to those of the anterior excepting for a somewhat stronger 

 development, the mmiber of teeth being four or five instead of three or four, 

 an additional small tooth being added. The minor hooks in uncini of the middle 

 region tend to be carried farther distad, more elevated. The large hook is 

 distinctly fibrillar, and, though the fibrillae are less conspicuous than those of 

 the neck, they may commonly be traced nearly to the apex. The smaller hooks 

 are also fibrillar. The subrostral bristles numerous, attached about, and for a 

 considerable distance proximad of, the subrostral angle, long. 



Localities. Off Panama: Sta. 3361 (Type-locality). Depth 1,471 fms. 

 Bottom of Globigerina ooze. 25 February, 1891. Several broken specimens, 

 of which the tji^e is complete excepting that the anal funnel is separated 

 from the body. 



Off Mexico: Sta. 3415 (lat. 14° 46', long. 98° 40'). Depth 1,879 fms. 

 Bottom of green mud and Globigerina ooze. 10 April, 1891. From this Station 

 the anterior ends of four incUviduals, with pieces of various other portions, 

 and numerous tubes. 



This species is readily distinguished from all others by the different structure 

 of the uncini and capillary setae, as also by the details of the head-plate. 



The tubes from Sta. 3361 consist of the usual tough, hyaline, lining membrane, 

 and a wall of soft, loose, greyish mud composed largely of the shells of Radiolaria 

 entire or in fragments, Globigerinae, and the frustules of diatoms, largely of 

 the characteristic marine discoid forms. The mud of the tubes from Sta. 3415 

 is more compact and is composed on the whole of smaller pieces, there being 

 fewer entii-e shells and more fine granular fragments. In these, diatom frustules 

 are numerous. 



SoNATSA, gen. nov.^ 



Head-plate comparatively long. Anterior tip relatively narrow and long. 

 Lateral free borders long, distinctly separated from the caudal division by an 



' Gosiute, soma, or in combination, so, many, and natsani, natsa, hook. 



