1911.] NATURAL SCIENCES OF PHILADELPHIA. 311 



fathoms, gray sand and rock; 4,334, same locality, 514-541 fathoms, 

 green mud and fine sand; 4,436, off San Miguel Island, 264-271 fath- 

 oms, green mud; 4,452, 4,453, 4,454, off Point Pinos Lighthouse, 

 Monterey Bay, 49-71 fathoms, green mud, sand and gravel; 4,457, 

 same locality, 40-46 fathoms, dark green mud; 4,464, 4,467, same 

 locality, 36-54 fathoms, soft dark mud; 4,4S0, off Santa Cruz Light- 

 house, 53-76 fathoms, dark green mud and sand; 4,548, off Point 

 Pinos Lighthouse, 46-54 fathoms, coarse sand, shells and rocks; 4,550, 

 same locality, 50-57 fathoms, green mud and rocks. 



Arioia nuda sp. nov. PI. XXI, figs. 172-176. 



As usual in the genus, this is a very fragile worm, and no complete 

 examples are known, but only four short anterior ends and a fragment 

 from near the caudal end. The type comprises two pieces not cer- 

 tainly belonging to the same individual: an anterior piece of 41 

 segments, 31 mm. long, 5 mm. wide and 3.2 mm. deep at somite VIII, 

 and a much more slender and gently tapered piece of 72 segments and 

 evidently from near the caudal end. 



Prostomium mammilliform or flattened dome- shaped, bearing a 

 blunt, nipple-like apical palpode about one-half as long as the prosto- 

 mium, the combined length of both being about equal to the basal 

 width of the prostomium. An obscure, rather large pigment spot 

 or eye at each side close to the base of the palpode. On the ventral 

 side a pair of parallel longitudinal grooves include between them a 

 slightly depressed area ending at the quadrate mouth which is bounded 

 on the sides by the peristomium and behind by a lip derived chiefly 

 from somite II. 



Anterior end of body for the first fifteen segments depressed, dis- 

 tinctly wider than deep, both dorsal and ventral surfaces moderately 

 convex. Segments increase rather rapidly in width to VIII or IX, 

 then become more gradually narrower. They are generally from four 

 to six times as wide as long. At XVI, coincident with the shifting 

 of the parapodia dorsad, the segments become much shorter, deeper, 

 much more strongly convex below and flatter above. These conditions 

 are maintained in the slender posterior region. There is no trace of 

 the pectinated ventral fold or ventral rows of papillae characterizing 

 the more typical species of the genus. Walls of anterior part of body 

 firm, of posterior region rather soft and translucent. Pygidium 

 unknown. 



Parapodia begin on I and are biramous throughout, the first fifteen 

 differing from the others in the lateral position and large size of the 

 neuropodium and the fimbriated or pectinated postsetal membrane. 



