NEW ECHIUROID AND SIPUNCULOID WORMS—FISHER 359 
Interiorly the strong longitudinal muscles form closely placed 
ridges much higher (5 mm.) than thick (1 mm). The ring muscles 
and entrances to skin canals cannot be seen unless these are spread 
apart. In S. nudus the ring muscles and skin-canal pores are ordi- 
narily visible when the dissection is pinned out flat. The short 
retractor muscles are free from one another. The origin of the 
ventral, slightly in advance of dorsal, is from muscle bands 2-5; 
and of the dorsal from 12-16. The grooves between the muscle 
bands continue, in shallower depth, upon the retractors. The rec- 
tum passes mesially between these two dorsal retractors and opens a 
short distance in front of their origin. From each side of rectum a 
short strong muscle (not fan-shaped as in polymyotus) is fastened to 
the longitudinal muscles at base of dorsal retractors. Selenka’s 
“Zottenbildung” is reduced to a mere filament. No spindle muscle. 
The curious posterior and anterior loops of the postesophageal 
intestine (a generic character) are more like those of nudus than of 
polymyotus. In the latter species the anterior loop (z) is attached to 
the right side of the body, not to both sides as in nudus and galapa- 
gensis. An inconspicuous ciliated groove is present in the esophagus 
but does not reach the coecum as in nudus and polymyotus. The 
intestinal spiral is too macerated for one to determine where the 
groove ends. 
The nephridia are slender free tubes 80 mm. long. There is a 
slight forward diverticulum at the base above the broad nephrostome. 
The nephridiopore opens between the fourth and fifth muscle bands. 
On each side of the base of the nephridium the muscle bands have 
thin, lobed crests (pl. 11, fig. 2). 
The dorsal and ventral blood vessels lack papillae and extend 
slightly beyond the mesenteries that anchor the esophagus to the dor- 
sal retractors; the esophagus is not attached to the ventral retractors. 
Anteriorly the nerve cord is held between two strong paraneural 
muscles, which are derived from the crest of the first longitudinals, 
with which the paraneurals merge behind the introvert. The brain, 
like that of polymyotus (and unlike that of nudus), has a large cere- 
bral organ consisting of two very irregular, folded sheets of tissue. 
The brain is less conspicuous superficially than in polymyotus. 
Color in alcohol, uniform yellowish brown. 
Type.-—U.S.N.M. No. 20835. 
Type locality—tIndefatigable Island, Galapagos Islands, Pinchot 
South Seas Expedition, July 8, 1929. From stomach of fish. 
Remarks.—This species has the same number of muscle bands as 
S. multisulcatus W. Fischer (1913, p. 93, Santos, Brazil), which differs 
in having rows of dark pigment spots in the longitudinal furrows; 
dorsal retractors span muscle bands 16 to 18; nephridia open six 
758332—47—2 . 
