1917] Essenherg: New Species of Polynoidae 55 



lies in the shape of the parapodia and in the number and shape of 

 the setae. In Halosydna carinata, of which Dr. J. P. Moore kindly 

 loaned to me an imperfect specimen for comparison, the notopodia 

 are small but prominent, being distinctly differentiated, while in 

 Halosydna macrocephala the notopodium is inconspicuous and hardly 

 differentiated. The neurosetae in Halosydna carinata are few, 10 

 to 20. They are strongly serrated, the plates with the serrations 

 extending to the tip of the subterminal tooth ; in Halosydna macro- 

 cephala the neurosetae are more numerous, (40 to 60) tlie subterminal 

 tooth is less prominent and the serrations do not extend nearly to the 

 subterminal tooth, leaving a considerable portion of the distal end of 

 the setae smooth. The notosetae in Halosydna carinata are few, only 

 3 to 4, short, barely reaching to the tip of the notopodium, curved 

 and ending bluntly. In Halosydna macrocephala the neurosetae are 

 numerous, (30 to 40) of two kinds, and long, reaching nearly to the 

 tip of the neuropodium. The 12 to 15 short setae are strongly ser- 

 rated, curved, and end bluntly (pi. 3, fig. 31). The twenty or more 

 fine notosetae are covered with fine serrations and are terminating in 

 a fine capillary tip. 



The setae of Halosydna macrocephala resemble those of Halosydna 

 californica, Johnson, but the shape and the relative size of the pro- 

 stomium and the deeply grooved palpi of Halosydna macrocephala 

 distinguish the species from Halosydna californica. 



Occurrence. — The locality of the type is unknown. Two incom- 

 plete specimens, the paratypes were found July 17, 1901, off San 

 Diego, lat. 33° 36'9 N; long. 118° 147 W. at a depth of 39-51 meters, 

 on rockv bottom. 



