NO. 4 HARTMAN : POLYCHAETOUS ANNELIDS 435 



Distribution. — Central California south to Guaymas, Mexico; also 

 San Clemente and Santa Cruz Islands off southern California and Cedros 

 Island off Lower California. Its bathymetric range is low intertidal to 

 65-80 fms. 



Dasybranchus platyceps, new species 

 Plate 55, Figs. 1-5 



Collection. — Sonora, Mexico in the Gulf of California, shore (3). 



There are fragments of 3 large individuals though none is apparently 

 complete. The pieces are much twisted and turned so that measurements 

 of lengths are only approximate. A long, posterior, tapering end measures 

 10 cm long for 180 segments. A larger anterior end with thorax and 70 

 abdominal segments measures 14 mm to the end of the thorax and 43 mm 

 long through 83 segments. Greatest width is about 8 mm in the posterior 

 thoracic region. The segments throughout are very short and broad as 

 though much contracted from preservation. Total number of segments 

 may be well over 200 and the entire length (preserved) may be 6 inches 

 or more. 



The thoracic segments are distinctly biannulate, the 2 rings about 

 equally long; parapodial fascicles arise from the posterior ring. The first 

 few abdominal parapodia are likewise biannulate and resemble those 

 in the last thoracic region but farther back in front of the origin of the 

 branchiae, the segments come to be gradually smoother and uniannulate 

 except for short transverse grooves at the sides of the body. In a post- 

 median region the segments are again more or less sharply biannulate and 

 faintly longitudinally ridged. 



Separation between thorax and abdomen is not distinct in external 

 view except for the obvious change in parapodia from setal fascicles to 

 long uncinal ridges. There are 13 setigerous segments; each is provided 

 with only pointed setae in both notopodia and neuropodia. 



The prostomium is a depressed, broadly rounded lobe; it lacks a pal- 

 pode and visible eyespots but the nuchal slits may be seen by pushing back 

 the peristomial fold. The peristomium is a long, biannulate ring that is 

 nearly 3 times as long as the first setigerous segment. The proboscis is 

 not everted in any specimen but by dissection it is seen to be coarsely and 

 closely papillated on its proximal half and smooth distally ; the separation 

 between the 2 regions is abrupt. 



