ON A NEW ENTEROPNEUST FROM MISAKI. 



81 



makes a thick envelops over the central complex 1 ; the anterior end of 

 the stomochord bends dorsali y in a remarkable manner ; lateral pouches 

 extends themselves ventro-laterally ; pericardium is produced into two 

 short anterior horns 2 , each accompanied by the corresponding half of the 

 glomerulus ; Muscle fibre bundles along the inner surface of the peri- 

 cardial wall fall in four distinct layers 3 — a ventral (dorsal to the central 

 blood sinus), a dorsal and two lateral ; nuchal skeleton has a prominent 

 carina, two parallel crests, and 

 short alary processes. 



Collar : — Collar - canals 

 parallel to the body axis ; 

 collar-pores open, on each side, 

 into the common cavity of the 

 most anterior four gill-pouches 

 (Fig. 3, cc.) ; dorsal septum 

 extends from the first root of 

 the collar nerve-cord up to the 

 posterior end of the collar 

 cœlom : perihaemal spaces 

 make together three dorsal 

 grooves — two deep lateral and 

 a shallow median — to clasp 

 the ventral surface of the collar 

 nerve-cord. 



Sagittal section through the common civity of the most 

 Trunk : — gill - pOUcheS anterior four gill pouches with the collar-pore at the anterior 



wall of the cavity. 



have no ventral cœcum and c. collar-ccelom, cc. collar-canal, cgp. common gill-pouches, 

 , . . . co. circular vessel, gc. gut cavity, pph. peripharyngeal space, 



the mOSt anterior four pairs spn . 3p Unchnic nerve fiber layer, r. trunk cavity. 



Fi?. 3. 



1. ) The same structure occurs in Glossobalanus sarniensis and Balanoglossus australiensis 

 (Spengel's Monograph, p. 101 and Hill, 1894 p. 9.) 



2. ) Bifurcation of the pericardium is one of the characteristics of the Glandicipitidae, 

 and in the Ptychoderidae we have only a parallel case in Glossobilanus ruficollis (Willey, 

 1899, p. 258.) 



3. ) They never make such a circular muscle layer as were suggested by Spengel 

 (Monograph, p. 169 and p. 511.) 



