370 Prof. Allman on the Construction and 
6. Monocautos*, Allman, nov. gen. 
Trophosome.—Polypite solitary, borne on the summit of a 
simple rooted hydrocaulus ; both hydrocaulus and hydrorhiza 
invested by a very delicate periderm; polypites flask-shaped, 
with two sets of filiform tentacles,—a proximal set longer and 
thicker, and arranged in a single verticil near the base of the 
polypite, and a distal set shorter and thinner, and scattered over 
a zone close to the summit of the polypite. 
Gonosome.—Gonophores adelocodonic, on simple or branched 
peduncles, which spring from the body of the polypite at the 
distal side of the longer tentacles. 
Monocaulos glacialis, Sars (sp.), = Corymorpha glacialis, Sars. 
Monocaulos pendula, Agass. (sp.),= Corymorpha pendula, Agass. 
7. Nemopsts, Agassiz. 
Trophosome.—Polypite free, conical, with two verticils of fil- 
form tentacula—a proximal near the base, and a distal near the 
apex; periderm absent. 
Gonosome.—Gonophores phanerocodonic, on short simple 
peduncles which spring from the body of the polypite between 
the two verticils of tentacula. Umbrella deep bell-shaped; ma- 
nubrium of moderate size, and furnished with four dichotomously 
branched oral tentacles ; radiating canals four, each terminating 
in a marginal bulb, while from every marginal bulb a tuft of 
tentacles is given off, two of the tentacles in each tuft being 
clavate and but slightly contractile, the rest filiform and very 
contractile, every tentacle carrying a distinct ocellus at its base. 
The generative elements are developed in four lobse, which 
spring from the base of the manubrium and thence extend for 
some distance along the course of the radiating canals. 
Nemopsis Gibbesit, M‘Crady. 
8. AcauLis, Stimpson. 
Trophosome.—The entire trophosome consists of a solitary, 
free, subfusiform polypite, which, at a later period, becomes at- 
tached by its proximal extremity; tentacles of two kinds,—one 
filiform, forming a single verticil near the proximal extremity, 
and subsequently disappearing—the other“capitate, and scat- 
tered on the body of the polypite towards its distal extremity ; 
periderm absent. 
Gonosome.—Gonophores phanerocodonic, springing from the 
body of the polypite between the filiform and capitate tentacula. 
Form of the Medusa unknown. 
_ Acaulis primarius, Stimpson. 
* From povos, single, and xavdbs, a stalk. 
ni? a 
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