REPORT ON THE SIPHONOPHOR^E. 183 



slightly concave, smooth, and probably directed (as in Hippopodius) obliquely down- 

 wards and outwards, in the vertical position of the axis of the nectosome. The opposite, 

 almost parallel, apical face is also smooth, more concave, directed oblicpiely upwards and 

 inwards ; it contains the axial groove, which is limited by the two prominent lateral 

 wings; it passes over downwards into the odd ventral face (fig. 13), which appears 

 bisected by the lowermost part of the axial groove, limited by the two descending ventral 

 teeth (the lowermost parts of the two axial wings). 



The dorsal face of the nectophore (fig. 14) is convex, broad and depressed, and 

 bisected by the prominent sagittal crest, which divides it into two paired lateral facettes, 

 densely covered with conical spines (figs. 11, 12). Two strong paired frontal teeth, with 

 a triangular spiny outside (fig. 9), separate the two dorso-lateral facettes from the two 

 ventro-lateral ; these are smaller, rather smooth, and separated one from another below 

 by the smaller odd ventral face. 



The five edges of the prismatic nectophore, which separate its five lateral faces, 

 correspond to the four edges of the exumbrella of a bilateral Medusa. The odd dorsal 

 edge, prominent in the sagittal median line of the dorsal face, is strongly dentate. The 

 opposite ventral edge is divided by the lower part of the axial groove into the two 

 ventral teeth, which embrace the stem. On both sides, to the right and left, are widely 

 prominent the two triangular, strongly dentate, lateral apophyses which are placed 

 at the opposite poles of the frontal axis ; they separate the two dorso-lateral facettes 

 from the two ventro-lateral faces, and correspond to the two lateral dorsal teeth of 

 Polyphyes. 



The numerous spines which cover the free outside of the nectophores (dorsal and 

 lateral faces) are mammillate or flatly conical, with a small apical point. Their number 

 amounts in each nectophore to more than a hundred. 



Nectosac. — The subumbrellar cavity is very small, scarcely half as long and broad as 

 the basal face of the nectophore, of which it occupies the axial or inner half (figs. 11, 12). 

 Its wide ostium is reniform, with a deep median notch at the ventral side. The muscular 

 plate of its shallow cavity is weak, the crescentic or sickle-shaped velum is rudimentary 

 at the ventral side, more developed on the two lateral sides. The nectocalycine duct, 

 which enters through the axial pedicle into the nectophore, gives off a blind pallial canal 

 in its dorsal part (fig. 12, ce), and divides at the top of the nectosac into the four radial 

 canals ; three of these (the dorsal and the two lateral) are very short ; the fourth (ventral) 

 canal (cv) is long, and expands near the circular canal in form of a broad two-winged 

 ventral sinus (figs. 11, 12, cv"). The concave dorsal edge of this sinus is smooth, 

 whilst the convex ventral edge is much longer, and irregularly denticulate. 



