414 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 10 



condition of both fang and teeth is unique to this species. The hood 

 likewise departs widely from that in other species in that it is high, 

 voluminous, and has a large aperture that perhaps leaves much of the 

 beak exposed even when the hooks are retracted in the paraoodium; its 

 distal free edge is finely serrated. The cleft is short. The shaft is finely 

 and closely fibrillated into the beaked end. The great distance between 

 the node and base of the hood is noticeable in this species. Its large hood 

 is to be compared only with that in A^. lobatus (see below). 



The posterior end of the body tapers and terminates in a simple, 

 collarlike ring without caudal appendages. Color in life is deep reddish 

 brown; branchiae are dark red. 



Notomastus magnus is characterized in having an areolated thorax 

 with conspicuous lateral organs on all segments. Abdominal neuropodial 

 tori are long and the 2 of a pair approach each other midventrally. 

 Nephridial apertures are present only in the abdomen. Genital apertures 

 in mature individuals are large and well developed on the first 20 to 24 

 abdominal segments. Retractile branchiae are bushy tufts; they arise 

 from the posteroectal margin of the notopodial tori; they are present 

 from about the twenty-sixth abdominal segment and continued posteriorly 

 perhaps to the end. Hooded hooks are unique m that the lower main 

 tooth is comparatively small and flat and partly surmounted by a double 

 caplike structure, with a short transverse row of teeth on its outer side 

 and sculptured with 18 to 22 crenulate ridges on its inner surface. It 

 differs from other species of Notomastus particularly in the character of 

 the branchiae and the distal ends of the hooded hooks. 



These numerous individuals are believed to be conspecific with a col- 

 lection of 6 individuals that originated from intertidal zones in San 

 Diego Bay, California, reported as Dasybranchus giganteus (Moore, 

 1909, p. 279). Although actual comparison of individuals has not been 

 possible, they are believed to be different from the Alaskan, deep-water 

 species, Notomastus giganteus Moore ( 1906, p. 227). The former were 

 described as follows: the protruded proboscis is subglobular, with 8 sul- 

 cated, radiating lobes and a closely granulated basal ring; thoracic seg- 

 ments are areolated on the surface; abdominal segments have neuro- 

 podial tori with extensive low ridges that become more elevated dorsally 

 and end abruptly in a prominence ; above them is the small but distinctly 

 rounded, ovoid lateral organ. The very small notopodial tori are dorsal 

 and connected across the dorsum by a low transverse fold ; posteriorly they 

 become very obscure. Branchiae are conspicuous bushy tufts of 20 to 30 



