1911.] NATURAL SCIENCES OF PHILADELPHIA. 255 



Within areas of similar size and under similar conditions of collecting 

 one usually finds not over four or five species. Three species were 

 found each at station 4,387, in deep water off the Gulf of Santa 

 Catalina, and 4,510, in Monterey Bay. With few exceptions, they 

 occurred on muddy bottoms. 



Nothria iridescens Johnson. 



Noihria iridescens Johnson, Proc. Bos. Soc. Nat. Hist., XXIX, p. 408, 

 PI. S, figs. 86, S7; PI. 9, figs. 88-92. 



The gills of this species begin on the first parapodium. Two points 

 in Johnson's description require modification after a study of the 

 large number of specimens in this collection. The biarticulate style 

 of the posterior paired tentacles is accidental and inconstant. Similar 

 breaks may occur on any of the styles; there may be several on one 

 style or be asymmetrical on the two styles of a pair or, as is most 

 usual, altogether absent. Neurocirri do not disappear on V, but 

 remain quite prominent, though short and thick, to VII, and their 

 thickened bases continue as glandular swellings to the middle of the 

 body as in many other species of the genus. The posterior paired 

 tentacles, although quite variable in length, seem always to exceed 

 the median tentacle. The color is quite variable, but usually more or 

 less blotched with deep purple and brightly iridescent anteriorly. 



A tube of average size is 190 mm. long and 5.5 mm. in diameter, 

 the outer end being slightly larger than the inner. The larger end is 

 composed almost entirely of a very fragile wall of fine silt nearly 2 mm. 

 thick and lacks the tough membranous lining that extends through 

 the remainder of the tube. 



This species occurs generally throughout the region covered by this 

 report and was taken in abundance at stations 4,462, 4,485, 4,508, 

 4,510, 4,523, 4,525 and 4,526. 



Stations 4,322, Soledad Hill, Point La Jolla, vicinity of San Dieg'o, 

 110-199 fathoms, soft green mud; 4,339, off Point Loma Lighthouse, 

 vicinity of San Diego, 289-369 fathoms, green mud; 4,433, off Santa 

 Rosa Island, 243-265 fathoms, green mud; 4,436, off San Miguel 

 Island, 264-271 fathoms, green mud; and the following stations in 

 Monterey Bay: 4,446, 4,457, 4,461, 4,462, 4,463, 4,464, 4,475, 4,482 

 4,485, 4,508, 4,510, 4,522, 4,523, 4,524, 4,525, 4,526, 5,428 at depths 

 varying from 36 to 357 fathoms, except in the case of the last station 

 where the depth is recorded as 766-800 fathoms. The bottoms were 

 muddy, usually "soft green mud," except at station 4,463, which was 

 rocky and yielded a single specimen, and at station 4,522, which 

 yielded ten specimens and is recorded as of gray sand and shells, 

 though evidently adjoining a bed of green mud (station 4,523, etc.). 



