20 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 27 



Affinities: Gnathia trilobata differs from G. tridcns of Menzies and 

 Barnard (1959) in the presence of a longer frontal projection, and in 

 other characters. It differs from G. productatridens, which it resembles 

 most, in the lack of crenulations and setae on the outer marginal notch 

 of the mandibles. No setal hairs arise from the mandibles and the telson 

 is without setal spines. 



VALVIFERA 



ARCTURIDAE 



Microarcturus Nordenstam 



Microarcturus tannerensis, n. sp. 



(Plate 14) 



Diagnosis: Eyeless, pigmentless. Body, including proximal segments 

 of peraeopods, covered wnth minute hairs. Whole body covered with 

 projecting calcareous spines bearing large beadlilce spheres. Cephalon 

 and peraeonal segments with at least two large dorsal projecting spines 

 and several dorsolaterally projecting spines. Last two peraeonal and 

 first two pleonal segments with transverse row of at least six spines. 

 Pleon of three segments, one being only partially separated from the 

 pleotelson. Pleon shorter than last four peraeonal segments and with 

 pointed posterior margin. Pleotelson with many short spines similar to 

 those on peraeon. Two most lateral and posterior spines with large 

 setae. First peraeopod somewhat chelate, bearing many sensory setae on 

 inside margin and large spines on outside margin. First antenna with 

 only four segments; distal segment dorsoventrally flattened, tipped with 

 many setae and three times as long as preceding segment. Second an- 

 tenna shorter than body, with each peduncular segment longer than pre- 

 ceding, ending in three increasingly shorter flagellar articles. Maxilliped 

 with strongly curved palp carrying many plumose setae. Mandible with 

 toothed incisor. 



Measurements: Holotype female 5.5 mm long. 



Type locality: 6832(1) ; Tanner Canyon; 1298 m; Jan. 28, 1960; 

 green mud. Lat. 32° 33' 36"N, Long. 118° 55' 40"W. 



Affinities: In general appearance the new species is most like Mi- 

 croarcturus digitatus Nordenstam (1933), except that the spines do not 

 end in a point but have a beadlike tip. Spinal armature is most like that 

 of Antarcturus brunneus as pictured by Nordenstam ( 1933) . 



