1911.] NATURAL SCIENCES OF PHILADELPHIA. 297 



ulum is directed dorsad and is most strongly develo])ed on the dorsal- 

 most setae which are also the longest. On anterior parapodia the 

 margins of the setae are smooth or nearly so (fig. 146); farther back 

 the serrations become more prominent, especially on dorsal setap, which 

 also have a few transverse pectina^ at the base of the geniculum (fig. 

 147). 



Jaws of two specimens dissected. Mandibles (PI. XX, fig. 148) dense 

 opake black, the posterior half or two-fifths narrow and somewhat 

 tapered, separated on the two sides by a wide median space, the 

 anterior portion abruptly twice as wide, the two halves united by an 

 extensive suture, the exposed tips slightly divergent with finely den- 

 ticulated free margins. Maxillae (Plate XX, fig. 149) also dense opake 

 black, the forceps jaws supported by a pair of small triangular carriers 

 prolonged into tapered filaments about one and one-third times as 

 long as the series of jaws, the forceps with massive bases and short, 

 strongly hooked ends, the left bearing on its medial margin eight or 

 nine stout teeth of diminishing size, the right about seven smaller 

 teeth. ^Maxillae II asymmetrical, the left short and stout with eight 

 teeth, the right long and narrow with about thirteen teeth diminishing 

 in size from before backward. IIP is a curved piece bearing two 

 teeth on each side; IV is irregular with five or six uneciual teeth; V 

 is also irregular with four or five slender teeth and the most anterior 

 (VI) is a small piece with one slender tooth and a bifid base. A long 

 ribbon-like band of chitin exceeding the forceps filaments in length 

 extends caudad from the posterior maxillae ventral to the forceps 

 carriers. 



In color some are pale gray and unspotted, but three of the specimens 

 are blotched with three dorsal series of dusky bluish spots and the 

 peristomium is deeply pigmented above. The cuticle is more or less 

 iridescent. 



Known only from station 4,496, Monterey liay, off .Santa Ci-uz 

 Lighthouse, 10 fathoms, fine gray sand and rocks. 



From Aracoda cerulea Schmarda. as redescril)ed by T^hlers, this 

 species is abundantly separated, particularly through the characters 

 of the jaws, which in fact depart materially from the form tj^Dical of 

 the genus. 



Arabella attenuata Trcadwell? 



Arahclln atlenuaia Treadwcll, liuU. U. S. Fish Comm., XXTII, )>:ut III 

 (1906), p. 1172, fig. 62. 



A small portion of the middle of a large specimen about :> nnn. in 

 1 Through an oversight maxilla III was overlooked in labeling fig. 149. 



