﻿April, 1857.] 



ELLIOTT SOCIETY. 



149 



The genus Pennaria is the only Endostome having a symmetrically 

 branched polypidom for its fixed larva. 



WILLSIA. Forbes. 



The characters of this genus are a rather shallow bell for one 

 of the Endostomata; a mouth surrounded with leaf-shaped labial 

 tentacula, or a simply undulated movable margin; rather short 

 digestive trunk, around which are placed the sexual glands; four 

 or six radiate tubes which bifurcate near their origin, the branches 

 thus formed again bifurcating before reaching the marginal tube, 

 at which point is appended a single tentaculum to each branchlet 

 of the radiate tubes; the tentaculum has a sessile bulb. Between 

 every two tentacula passes upward on the outer surface of the 

 disk, a structure resembling a knotted cord, consisting apparently 

 of a delicate, superficial, membraneous tube, which widens at 

 intervals, to contain groups of thread-cells. Forbes has de- 

 scribed a complicated ocellus, but I have been unable to find 

 that any such existed on the colored bulb of the tentaculum. 



Larva unknown. But the shallow bell and short digestive 

 cavity of Willsia seem to bring it into the neighborhood of Chry- 

 somitra. I have placed it, provisionally however, in this group 

 near Cladonetna, on account of its branching circulatory tubes. 



Distribution. — British Seas and Charleston harbor. 



WILLSIA ORNATA, nov. spec. 

 PI. 9, Fig. 9-11. 



The form of the bell is rather more conical than that of W. 

 stellata (Forbes,) bluntly pointed above; the mouth is surrounded 

 with only an undulating frill-like margin, which I never saw 

 assume the appearance of being divided into arms. The digest- 

 ive trunk short and stout; radiate tubes only four in number ; ten- 

 tacula sixteen, rather short, lashes having a roughened surface. 

 In the frill-like border of the mouth are implanted a series of 

 large, oval, light-refracting bodies, which have the appearance of 

 thread-cells, and in which I have at times thought I had detected 

 the coil of the thread, but could never satisfy myself of it. They 

 are much larger in proportion to the animal than thread-cells 

 usually are in these medusae. The same may be said of the pecu- 

 liar rows of cells mentioned in the analysis of the genus, though 

 these are rather smaller than those around the mouth. The 

 arrangement of these bodies is peculiar, and a group of them in 



