Diam. 



PLATE XLV1. 



Porpitella pectanthis, u. sp. (p. 64). 



Figs. 1, 2. The complete corm, seen from above iu the right half (1), from 

 below in the left half (2). In the centre is visible the mouth of 

 the sterile central siphon, surrounded by a corona of sixteen small 

 gonostyles (or sexual siphons). The right half of the figure (l) 

 shows the half of the radiate pneumatocyst, with eight marginal 

 lobes. The margin of the umbrella is beset with a series of glands 

 (dark points) and surrounded by a corona of numerous tentacles, 

 composed of sixteen radial bunches, . . . . x 4 



Fig. 3. Vertical meridional section through the lenticular biconvex umbrella 

 and its appendages, ph, Central chamber of the pneumatocyst ; 

 pq, one of the eight radial chambers ; ph, concentric ring- 

 chambers ; urn, limbus umbrella? ; t, tentacles ; uc, centradenia ; 

 cm, hepatic vessels ; st, gastrobasal plate ; sa, central siphon , 

 so, its mouth, . . . . • • . x 8 



Fig. 4. Kadial segment of the pneumatocyst, seen from above ; highly 

 magnified, po, Central stigma ; pe, peripheral stigma ; ph, 

 central chamber; pq, radial chamber; ph, concentric ring-chambers; 

 pg, pneumothyrae (pori communicantes), . . . x 40 



Fig. 5. Radial segment of the pneumatocyst, seen from below ; highly 

 magnified, ph, Central chamber ; pq, eight radial chambers ; 

 pe, their stigmata (shining through) ; pt, tracheae ; ph, concentric 

 ring-chambers, . . . . . • . x 20 



Fi°\ 6. Vertical section through the centre of the umbrella. Characters as 



in figs. 3, 4. pt, Tracheae, . . . • . x 20 



Fig. 7. Vertical section through the peripheral part of the umbrella. 

 Characters as in figs. 3, 4. w, Subumbrella ; pt, trachea? ; us, 

 muciparous glands of the umbrella-margin, . . x 20 



Fig. 8. A portion of a single trachea, . . . . . . x 300 



