DISCOVERY REPORTS 



are inserted on the dorsal wall more posteriorly. In Nebaliopsis the groove muscles consist of a very 

 thick bundle of fibres passing from the dorsal ridge as mentioned above to the anterior wall of the 

 oesophagus ventral to the anterior median projection, while only four pairs of slender strands were 

 found in Nebalia. The anterior lateral dilators {l.dil.^ and l.dil.^) differ only in that they slope dorsally 



p.ddii 

 a.d.dil. 



a.h.m. 



y. arc. 



arc. 



3. oes. 



pj.dil. 



Fig. 6. Diagrams to show the musculature of the fore-gut of: A, Nebalia; B, Nebaliella; C, Nebaliopsis. a.d.dil. anterior 

 dorsal dilators; a.h.m. muscles of the anterior horns of the stomach; a.m. median anterior muscle; a.oes. anterior oesophageal 

 muscles; a.s.m. small anterior muscles; conl. strong contractor muscle; c.p.m. cardio-pyloric muscles; d.ca. dorsal caeca; 

 d.dil. dorsal dilator; d.gl. digestive glands; d.s. digestive sac; h.circ. horizontal circular muscles; /. labrum; l.dil.^, l.dil.^, 

 l.dil.^, l.dil.^, and l.dil.^, points of insertion of the lateral dilators; m. mouth; m.p.m. median projection muscle ;/)a. paragnaths; 

 p.d.dil. posterior dorsal dilators; p.l.dil. posterior lateral dilators; p.m. posterior muscles; p.oes. posterior oesophageal 

 muscles; t.p.ni. muscles of the trilobed process; v.ca. ventral caeca; v.circ. vertical circular muscles ; v.l.dil. ventro-lateral 

 dilators; v.m. small ventral muscles. 



