NEW ECHIUROID AND SIPUNCULOID WORMS—FISHER 371 
PLATE 11 
Sipunculus galapagensis, new species 
1, Anterior half of type, natural size, opened a little to left of middorsal line 
and spread out; longitudinal muscle bundles and right nephridium omitted. 
2, Proximal end of left nephridium and adjacent muscle bundles, numbered, 
xX 5. 
3, Cerebral body or frons * 10. 
4, Tentacle crown, X 3. 
5, Marginal elements, enlarged. 
C, Coecum; N, left nephridium; NC, nerve cord; O, esophagus, 1 to 6 indicat- 
ing position of dorsal frenula; R, rectum with fixing muscle on either side; 
RD, dorsal retractor, RV, ventral retractor; X, anterior bend of forward loop 
of intestine; Y, where the intestine turns to form the forward loop; Z, 
rudiments of anal glands. 
PLaTE 12 
Xenosiphon branchiatum (Fischer) 
— 
, Anterior sixth of a specimen, with introvert extended, from Panama. It 
has been opened a littie to the left of middorsal line and spread out so that 
the dorsal retractors are unnaturally spread apart and the rectum is on 
extreme right instead of being in middorsal line. The esophagus actually 
bends to left and is attached behind and in a line with the left dorsal retrac- 
tor; X 2. Figures denote muscle bands to right and left of nerve cord. 
2, Sketch of another specimen from Panama, in which the introvert is partly 
withdrawn, to show altered position of protractors (P), natural size. 
, Brain and the bushy frons (cerebral organ), < 10. 
, Six dermal rectangles at margin of papularium of La Paz specimen, X 10. 
In this specimen the cuticular welts above the canals alone show well, the 
detail in upper left rectangle being supplied from a Panama specimen. 
The next rectangle has no papillae but the irregular canal shows through 
the cuticle. The lower left shows at each end of canal the pores (arrows) 
which lead eventually to coelom. 
, A single rectangle of skin of Panama specimen about 25 mm. anterior to 
papularium showing a skin canal gorged with material, X 20. At either 
end, the dark spot marks the canal to coelom. 
A, anus; C, intestinal coecum; CV, dorsal contractile vessel; CV’, ventral 
contractile vessel; F’r, cerebral organ or frons; J, introvert; N, nephridium; 
NC, nerve cord; O, esophagus, its mesenteries cross-hatched; P, protractors 
of head; R, rectum; RD, dorsal retractor; RV, ventral retractor; S, spindle 
muscle; 7’, tentacles; Z, filamentous organ described in text. 
1 oO 
or 
PLATE 13 
Siphonomecus mullicinctus, new species 
1, Region of origin of retractors, the end of esophagus, and rectum to show rela- 
tions of the two latter to spindle muscle, X 1. The frenulum, F’, is a 
branch of the spindle muscle, S; its cut end is attached to body wall dor- 
sally. Esophagus has been severed to show ascending spiral around spindle 
muscle. 
