124 THE VOYAGE OF H.M.S. CHALLENGER. 



Nectophore (figs. 9, 10, 11, nn). — The special nectophore, which contains no manu- 

 brium, occupies the ventral fissure of the bracteal cavity, in which only its basal part is 

 enclosed. The umbrella is a slender four-sided pyramid, distinctly bilateral, since the two 

 dorsal edges are stronger, and more prominent at the base, than the two ventral edges. 

 All these edges, and also the quadrangular basal edge, with the four prominent teeth, are 

 elegantly denticulate (fig. 17). The basal and ventral faces of the exumbrella are concave, 

 the dorsal and the two lateral faces convex. 



Nectosac. — The peduncular canal, which arises from the base of the phyllocyst, 

 enters through the obliquely truncate top of the nectophore, and divides on the top of 

 the muscular subumbrella (w) into four subregular radial canals (cr). These unite at the 

 ostium of the umbrella by a circular canal (cc) above the broad velum (v). 



Gonophores (fig. 11, hm; figs. 12-14). — The young Erssea compressor possesses, besides 

 the sterile nectophore, only a single gonophore, the older form two or three gonophores. 

 These are usually of the same sex (the cormidia therefore diclinic) ; but sometimes 

 a male and a female gonophore are present in the same Eudoxia (the cormidium there- 

 fore monoclinic). The umbrella (it) of the male, as well as of the female gonophores, is 

 slender ovate, with four edges which are smooth in the proximal half, elegantly denticu- 

 late in the distal half. They are prolonged over the mouth of the umbrella, and form 

 four prominent triangular teeth, the two dorsal teeth being larger than the two ventral. 

 The subumbrella (w) exhibits in the gonophores the same four subregular radial canals, 

 connected by a circular canal, as in the nectophore (figs. 9-11, nn). 



The male gonophores (fig. 11, hm; fig. 12) have in their umbrellar cavity a large 

 spindle-shaped or ovate spermarium (hm), with a wide central spadix (hx). 



The female gonophores (figs. 13, 14) exhibit an ovarium of very variable size (fm). 

 Sometimes the entire umbrellar cavity is filled with eggs (fig. 13), whilst, at other times, 

 only a few ova (four in fig. 14) occupy its proximal half. 



Genus 17b. LUtea, 1 n. gen. 



Definition. — Ersseidse with a hemispherical or mitriform rounded bract, without sharp 

 edges and without pointed apex. Phyllocyst small, with four radial canals arising from 

 its base. (Cormidia of the genus Lilyopsis f) 



The genus Lilsea comprises those Ersseidae which possess a mitriform rounded bract, 

 without sharp edges or apical point. Its form agrees with that of the eudoxomes of 

 Praya and Lilyopsis. A further resemblance to the latter is given by the fact, that 

 each cormidium possesses a sterile nectophore, the mouth of which bears a circle of 

 rudimentary tentacles and four red pigment-spots (ocelli) at the distal end of the four 

 radial canals. They are very similar to the medusiform special nectophores of Desmo- 



1 Lilsea (A/*a/«), name of a Naiad. 



