280 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 10 



C. mollis was originally designated type and only species of the genus 

 Metachone Bush (1904) and considered to have affinities with Euchone 

 Malmgren and Dialychone Claparede, but, since Euchone is character- 

 ized by its peculiar caudal end and Dialychone by its abdominal uncini in 

 which the secondary teeth are large, the affinities of C. mollis are un- 

 doubtedly with species of Chone Kroyer. C. mollis differs from C. in- 

 fundibuliforrjiis Kroyer, which is a larger species, and in life is often 

 spotted reddish or somewhat greenish. Also, spatulate thoracic setae in 

 the latter are gently rounded distally or have a minute mucron (pi. 23, 

 fig. 44, based on an individual from the west coast of Sweden). Thoracic 

 uncini have a comparatively thick major tooth (pi. 23, fig. 45), and 

 abdominal uncini have a thick basal plate (pi. 23, fig. 46). 



C. mollis constructs a closely fitting tube of mucus, externally covered 

 with fine sand particles; the occupant leaves it readily when disturbed 

 and can quickly reconstruct another. Originally described from Pacific 

 Grove, it ranges in intertidal zones of the northeast Pacific. 



Ghone minuta, new species 

 Plate 23, Figs. 50-52; Plate 24, Figs. 59, 60 



Numerous individuals were taken at Dillon Beach, in holdfasts of 

 algae and among compound ascidians. This is one of the smallest members 

 of the genus. Total number of segments of sexually mature individuals 

 (with large eggs in abdominal segments) includes 8 thoracic and 26 

 abdominal setigers; total length is about 10 mm, including the crown, 

 which measures 2 mm. Segments are clearly annulate; those of setigers 

 2 to 6 show faint transverse grooves dividing the ring ventrally into 2 

 nearly equal parts ; others are neatly uniannulate. 



The tentacular crown (preserved out of the tube) is expanded, shaped 

 like a bell, with barbless tips extending distally. There are 6 to 7 pairs of 

 pinnate radioles on each side, together with 3 pairs of filamentous radioles 

 at the dorsal ends of the crown (pi. 24, fig. 59). The barbed radioles 

 are united at their bases by a palmate membrane that extends distally 

 only about one third of the length of the radioles; the membrane is con- 

 tinued for some distance along the sides of the radioles but does not 

 extend to the barbless distal portion. Each radiole has, on its oral side, 

 about 24 pairs of barbs, in double rows. Palpi are elongate, triangular. 



The collar is smooth, entire, straight, about as long as the first 2 

 setigerous segments together. On its ventral side, medially, it has a slight 

 concavity, but extends around the peristomial ring as a trim collar to the 

 middorsum, where it is cleft and inserted on the peristomial membrane. 

 Eyespots are lacking. 



