1923] NATURAL SCIENCES OF PHILADELPHIA 197 



4464, off Point Pinos Lighthouse, 36-51 fathoms, soft dark gray 

 mud; 4467, off Santa Cruz Lighthouse, 51-54 fathoms, soft dark 

 gray mud; 4475, off Point Pinos Lighthouse, 58-142 fathoms, 

 soft green mud; 4485, off Santa Cruz Lighthouse, 39-108 fathoms, 

 soft green mud and sand; 4492, same locality, 26-27 fathoms, 

 soft green mud; 4522, off Point Pinos Lighthouse, 130-149 fathoms, 

 gray sand and shells; 4523, same locality, 75-108 fathoms, soft 

 dark mud; 4552, off Point Pinos Lighthouse, 66-73 fathoms, green 

 mud. Twenty-two at station 4485, 1 to 3 at the others. 



Pista sp.? 



Three specimens of another Pista, which may be new, are left 

 unnamed because their very poor state of preservation prevents a 

 satisfactory description. All three are incomplete and the largest 

 measures 5.2 mm. in maximum width. 



Gills three pairs, on II, III, and IV, with slender, spirally twisted, 

 erect, tapered stalks, which may be traced to the apex. Branches 

 eight to thirteen, arranged in a spiral, open below but crowded 

 and diminishing in size toward the apex. Each branch consists 

 of a closely crowded tuft of short filaments. As usual in this genus 

 the gills are asymmetrical and differ greatly in size. 



The wings, which are developed on somites I-IV, exhibit some 

 striking peculiarities. On I, they are very large, rounded, ventro- 

 lateral and bent forward at the sides. II bears an anterior ventral 

 fold only. From a similar but deeper and longer fold on III, 

 there rises just below the level of the gills, a long, prominent, 

 tongue-like extension with a slight spiral twist which reaches 

 forward to a point slightly in advance of the ])rostomium. The 

 wings on IV are small, subtriangular and project forward at the 

 same level as the free ends of the fold on II. 



Parapodia, setae and uncini have the distribution and form ty])ical 

 of Pista. 



Stations 4430, off Santa Cruz Island, 197-281 fathoms, black 

 sand, pebbles and rocks, 1 specimen; 4523, off Point Pinos Light- 

 house, 75 108 fathoms, soft dark mud, 2 specimens. 



Thelepus branchialis Trcadwell. 



In each of the gills the filaments are arranged in two transverse 

 rows. The number of filaments varies greatly, increasing with the 

 size of the specimen, those of the first pair having from 6 to 22, 

 the second, 4-16 and the third, 1-12. Setae begin on III and 

 continue for from 31 to 41 segments. Uncini may have either two 

 or three apical teeth above the fang. 



