86 ' . Morris and Raff : 



The gonads are arranged in a single series on the right side, 

 and vary in number from 25-30. 



The left metapleiir stops behind the atriopore ; the right is 

 continuous with the median ventral fin. 



2. — Pigment Ring. 



A very marked feature of the species is the presence of an 

 incomplete ring of pigment in the rostral fin. It is situated 

 about .6350 mm. from the tip of the snout immediately in 

 front of the first myotome, and is about .0635 mm. in thickness 

 (Fig. 11). The pigment material lies in the cuticle, and extends 

 dorsally and ventrally to varying distances in different speci- 

 mens. In some of the sections examined the pigment was con- 

 tinued right over the dorsal surface, and stops short ventrally, 

 thus forming an incomplete ring (Fig. 12). In others it did 

 not extend over the whole doisal surface, but continued fur- 

 ther ventrally into the oral folds for a short distance. It is 

 always present, however, as two thick bands on each side of 

 the body, and varies only in its extension dorsally and ven- 

 trally. The olfactory pit and eye spot lie in the ring of 

 pigment . 



Pigment material is also developed in the dift'erent spaces in 

 the body. In front of and in the region of the pigment ring 

 it is thickly developed in the dorsal and ventral portions of 

 the fin, and also in the spaces surrounding the notochord. 

 Beyond the ring the pigment surrounds the nerve cord and 

 notochord, and lines the dorsal fin space and the coelum. It 

 runs down the right and left portions of the oral hood, where it 

 is very thickly developed (Fig. 13). 



3. — Atrial Cavity. 



At the anterior end of the body the atrial cavity forms a 

 large space around the ventral and lateral regions of the 

 pharynx. It extends backwards surrounding the alimentary 

 canal, and separating the coelom from the body-wall, and 

 opens to the exterior by means of the atriopore about two- 

 thirds of the way down the body (Fig. 1). Beyond the atriopore 

 the cavity is continued back (F'ig. 2), and divides into two 

 caeca surrounding the intestine, and separating the coelom 



