Limitation of Genera among the Hydroida. 379 
the Medusa is produced directly from the egg without the interven- 
tion of a polypoid trophosome*. 
The absence of a trophosome affords a differential character of 
much importance ; and the name of Lzzzia must accordingly be con- 
fined to such Meduse as, with the form of Lizzia, are directly deve- 
loped from the egg, while it may be provisionally used for such as 
resemble them, but have not yet had the other terms of their life- 
series discovered ; the detection of these will determine the genus, 
Lizzia or Leptoscyphus, or possibly some other still, to which the 
provisionally named Hydroid may belong. 
Leptoscyphus tenuis, Allm. 
2. Larora, Lamouroux. 
Trophosome.—Hydrocaulus creeping and adherent, or erect 
and rooted by a filiform hydrorhiza; hydrothecz sessile on the 
hydrocaulus, or pedunculated, tubular, destitute of an opercu- 
lum. Polypites cylindrical, with the tentacular verticil surround- 
ing the base of a spherico-conical metastome. 
~ Gonosome.—Gonophores phanerocodonic. Medusz deep bell- 
shaped, with short manubrium, four radiating canals, and four 
marginal tentacles with bulbous bases, destitute of ocelli; tenta- 
eles alternately long and short ; lithocysts not present. 
_ Ihave described the Medusa on the authority of Agassiz. It was 
observed by Mr. A. Agassiz on a Hydroid which his father refers to 
the Lafoéa cornuta of Lamouroux. In this observation we have thus 
a second example of the production among the Campanularida of 
Medusz belonging to the type which is destitute of lithocysts and 
developes its generative elements in the walls of the manubrium. 
The first recorded instance was described by myself some years ago 
in Leptoscyphus tenuis. 
Lafoéa dumosa, Linn. (sp.), = Campanularia dumosa, Fleming, 
Johnst., = Calycella dumosa, Hincks. 
Lafoéa cornuta, Lamx. 
Lafoéa fruticosa, Sars, = Campanularia gracillima, Alder. 
Lafoéa plicatilis, Sars. 
Lineolaride. 
1. Lingoxarta, Hincks. 
Trophosome.—Hydrocaulus a creeping and adherent tube 
carrying the hydrothece from distance to distance along its 
length ; hydrothece sessile on the hydrocaulus, tubular, with 
the orifice subtriangular and armed with an earlike projection 
on each side. Polypites not known. 
Gonosome.—Gonangia large, oviform, and adherent, sessile on 
the creeping hydrocaulus. Gonophores not known. 
The genus Lineolaria was constituted by Hincks for a remarkable 
* See Claparéde in Zeitschr. f. wissens. Zool, Band x. 1860, 
25% 
