412 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 10 



N. sinuosus Grube (1877) from China, N. zeylanica Willey (1905, p. 

 287) from the Gulf of Manaar, and A^. annenkowae Zachs (1933, p. 

 130) from the North Japan Sea. 



Key to Species 



1. Abdominal hooks supposedly lack a hyaline hood. . . N. giganteus 



1. Abdominal hooks have a hood 2 



2. Branchiae retractile, forming full bifurcated tufts that emerge 

 from the posterior face of notopodia (pi. 50, fig. 6) present in 

 median and posterior abdominal segments . . .N. magnus 



2. Branchiae not retractile, consist of long filamentous structures 

 (pi. 51, fig. 4) that arise from median and posterior abdominal 

 neuropodia N. lobatus 



Notomastus magnus, new species 



Plate 50, Figs. 1-6 



Dasybranchiis giganteus Moore, 1909, p. 279, not Moore, 1906, p. 227 



(see below). 

 Notomastus giganteus Berkeley, 1941, pp. 48-49. 



Collections.— 9{)5-Z^ (posterior end) ; 1032-40 (6), 1130-40 (1); 

 1133-40 (fragment); 1142-40 (2); 1211-40 (many); 1252-41 (1); 

 1254-41 (1) ; 1265-41 (1) ; 1293-41 (1) ; 1294-41 (fragment) ; 1387-41 

 (1) ; 1441-41 (1) ; 1442-41 (3) ; 1457-42 (1) ; many others come from 

 northern, central, and southern California, from shore stations especially 

 in mud flat areas. 



Mature individuals are large and robust; the total length approaches 

 30 cm (presei-ved) for larger specimens. In the thorax the body is about 

 7 mm wide. The thoracic epithelium is areolated throughout but decreas- 

 ingly so in its posterior part (pi. 50, fig. 1). Lateral organs are present 

 on all thoracic and abdominal segments ; they are conspicuous in both 

 regions, but in the thorax they may be more or less withdrawn since 

 they are somewhat retractile as typical for these parts. They are located 

 at the sides of the body, between notopodial and neuropodial ridges and 

 slightly nearer the former. 



The prostomium is a short, flattened lobe with subglobular palpode 

 at its anterior end ; it lacks eyespots but the nuchal slits are clearly visible 

 near the posterior margin. The proboscis is coarsely papillated on its 



