PLATE XLVII. 



Porpema medusa, n. sp. (p. 61). 



Diam. 

 Fig. 1 . The medusif orm corm, seen from the exumbrellar or superior face. The central part of the 

 exumbrella exhibits the radial rows of stigmata in the pneumatocyst, whereas in the 

 peripheral part the forked branches of radial pallial canals are visible. The numerous 

 tentacles of the surrounding subinarginal corona are smallest in the uppermost row, . x 10 



Fig. 2. Lateral view of the same corm in profile. (Compare figs. 3 and 4), . . . x 10 



Fig. 3. Lateral view of the same corm, after removal of the tentacles, uu, Linibus umbrellas ; f, the 

 uppermost row of small tentacles ; tu, polygonal facettes where the numerous tentacles 

 have been attached to the subumbrella ; s.r, sexual siphons ; sh, central siphon ; sr, 

 proboscis; so, its mouth, . . . . . . . x 10 



Fig. 4. Vertical meridional section through the same corm. ph, Central chamber of the pneumato- 

 cyst; pk, its concentric ring-chambers ; x, gastrobasal plate ; tie, centradenia ; w, subum- 

 brella ; t, tentacles ; sx, sexual siphons; sh, central siphon ; sr, proboscis; so, mouth, . x 10 



Fig. 5. Central portion of the subumbrella, seen from below, sz, Central siphon ; so, its mouth ; sx, 



sexual siphons ; ;/, gonophores, . . . . . . . . x 20 



Fig. 6. Horizontal transverse section through the middle portion of the corm. uc, Centradenia ; 

 cm, its hepatic vessels ; cr, radial canals, running between eight chambered radial portions 

 of the pneumatocyst ; cz, coronal canal ; tu, insertions of the tentacles, . . . x 20 



Fig. ' 7. Central portion of the pneumatocyst, seen from above, ph, Central chamber ; p>1, eight 

 radial chambers ; pk, two concentric ring-chambers ; ]>r, radial furrows ; pe, eight peri- 

 pheral stigmata, . . . . . . . . x 20 



Fig. 8. Horizontal transverse section through the pneumatocyst and the uppermost portion of the 



centradenia (in the height of x in fig. 4). Characters as in figs. 6 and 7, . . x 20 



Fig. 9. Horizontal transverse section through the lowermost portion of the centradenia (uc). sf, 



Ostia gastralia (openings of the eight radial canals into the central siphon), . . x 20 



Fig. 10 Horizontal transverse section through the central siphon, with eight radial folds, d, Ento- 

 derm ; 2, fulcrum ; e, exoderm ; sc, gastral cavity, . . . . . x 20 



Fig. 11. Two muciparous glands of the umbrella-margin, . . . . . - x 400 



Fig. 12. A small portion of the umbrella-margin, cr, Radial canals ; us, muciparous glands, . x 200 



