Mollusca. descending perpendicularly. 
MOLLUSCA. 
The S. turgens of Phipps is 
~~" the type. 
Genus Sypneum.—Anal orifice simple and tubular. 
The body is inversely conical. The stomach surrounded 
with glands. Intestine spirally folded. Ovarium peduncu- 
lated. The S. twrbinatum is the only known species, and 
was sent to Savigny by Leach from the British seas. 
(B.) Body sessile, polymorphous. 
(a.) Each system with a central cavity. 
Genus Poryciryum.—Systems numerous, convex stellu- 
lar. Individuals arranged irregularly round the common 
centre. Abdomen inferior pedunculated, and less than the 
thorax. Ovarium single, pedunculated, and attached to the 
side of the abdominal cavity, and drooping. 
M. Savigny describes one species from the Mauritius, and 
five from the Gulf of Suez. 
(.) Systems destitute of the central cavity, and the an- 
gles of the branchial meshes without papille. 
Genus Atripium.—Individuals in a single row round the 
common centre. 
The thorax is cylindrical. The abdomen inferior, sessile, 
and of the size of the thorax. Ovarium single, sessile, pla- 
ced at the bottom of the abdomen, and prolonged perpendi- 
cularly. Savigny divides the genus into two tribes. In the 
first, the individuals are simply oblong, with an ovarium 
shorter than the body, as A. ficus (Alcyonium jicus, Linn.) 
In the second, the individuals are filiform, with an ovarium 
longer than the body, as A. effusum of Savigny, tab. xvi. f. 3. 
Genus Dmemnum.—Individuals in distinct systems. 
The thorax is short and subglobular. The abdomen in- 
ferior, pedunculated, and larger than the thorax. The anal 
opening is obscure. The ovarium is single, sessile, and 
placed on the side of the abdomen. D. candidum and vis- 
cosum, from the Gulf of Suez, are the only known species. 
2. Branchial Orifice simple. 
The species form a thin fleshy crust on stones and sea- 
weeds. The individuals are stellularly arranged in distinct 
systems. The branchial orifice is circular and undivided. 
The abdomen is sublateral, and fixed at the bottom of the 
branchial cavity. The intestine is small, and the anus in- 
distinct. The angles of the branchial meshes are without 
papilla. 
Genvs Borryiivus.—Systems furnished with a central 
cavity. The systems are prominent, and consist of one or 
more regular concentric rows. The ovarium is double, 
being attached to each side of the branchial sac. 
This genus is subdivided by Savignyinto Botryll stellati, 
and Botrylli conglomerati. In the first, where the indivi- 
duals are distributed in a single row, there are some species 
in which the individuals are cylindrical with approaching 
orifices, and the limb of the central cavity not apparent after 
death, and probably short, as the B. rosaceus, Leachii and 
Borlassii. In other species, the individuals are ovoid, with 
remote orifices, and the limb of the central cavity is always 
apparent and notched, as B. Schlosseri, stellatus, gemmeus, 
and minutus. In the botrylii conglomerati, in which the 
individuals are disposed in several rows, there is only one 
species, B. conglomeratus. 
Genus Evce.rium.—Systems destitute of a central cavi- 
ty- The individuals are distributed in a single row, and the 
ovarium is single, sessile, and attached to the side of the ab- 
dominal cavity. The H. hospitiolum of Sav. tab. iv.f. 4., is 
the only known species. / 
2. Tribe. 
Body free, and moving about in the water. 
Genus Pyrosoma.—The body is gelatinous, in the form 
of a lengthened bag open at the widest end. The individu- 
als are arranged perpendicularly to the axis of the central 
cavity, super-imposed on one another. The branchial ori- 
fice is external, without rays, and with an appendage over 
its upper margin. The anal orifice is opposite, and termi- 
nates in the central cavity. Branchial sac destitute of folds, Mollusca. 
with a membranaceous ring at the entry. The branchize === 
are disjoined. The abdomen is inferior to the branchiz, 
and not separated by any contraction. Liver distinct, glo- 
bular, and retained in a fold of the intestine. Ovarium 
double, opposite, and situate at the upper extremity of the 
branchial cavity. 
M. Savigny divides the species into Pyrosomata verticil- 
la, having the individuals arranged in regular prominent rings, 
as P. elegans of Lesueur; and Pyrosomata paniculata, hav- 
ing the individuals forming irregular circles unequally pro- 
minent, as P. giganteum and Atlanticum. 
2. Subdivision. Monochtonida. 
Inner tunic adhering throughout to the external one. 
The body is gelatinous, transparent, and simple. The 
branchial cavity is open at both ends, communicating freely 
with the anus. The branchial orifice is in the form of a 
transverse slit, with one edge in the form of a valve, to ac- 
celerate the entrance of the water into the cavity. The 
inner tunic is strengthened by numerous transverse muscu- 
lar bands, which, by contracting, diminish the diameter of 
the cavity, and eject the water from the anal orifice, there- 
by propelling the body through the water. The digestive 
organs are situate at the inner end of the cavity. The mouth 
and rectum are simple ; the former placed between the two 
branchiz, the latter directed towards the anal orifice. The 
heart is contiguous to the stomach, at the bottom of what 
may be termed the branchial sac, and is enveloped in a 
membranaceous pericardium. The branchiz are double, 
not incorporated with the walls of the sac, but with two folds 
of unequal length. The largest is free in the middle, fixed 
at each extremity, and opposed to the dorsal groove, and 
traverses the cavity obliquely. The other extends from the 
base of the first to the extremity of the dorsal groove. The 
surface of the branchiz consists of transverse vessels in a 
single range in some species, and a double range in others. 
When young, many individuals often adhere, and form 
chains and circles. But the fully grown individuals are al- 
ways detached and single. 
This subdivision comprehends the species of the genus 
Salpa; they are exceedingly numerous, and appear to be- 
long to many different genera. M. Cuvier has given indi- 
cations of some of these, chiefly derived from the shape. 
A few are furnished with an elevated crest or fin, as the 
Thalia of Brown ; a few have both extremities rounded or 
truncated, as Salpa octofera of Cuvier; others have one ex- 
tremity produced, as Holothuria zonaria of Gmelin; and 
even both extremities produced, as Salpa mazxima of For- 
skael. The Salapa moniliformis, so common in the Heb- 
rides, and first recorded as a native by Dr. Macculloch, in 
his valuable Description of the Western Isles, vol. ii. p. 188, 
and imperfectly figured in its young state, at tab. xxix. fig. 
2., appears to be closely allied to the S. maxima of Forskael, 
and but very remotely with the S. polycrateca and confeder- 
ata with which it is compared. This observer states, that 
“Tt cannot bear to be confined in a limited portion of wa- 
ter, as it died even in a ship’s bucket in less than half an 
hour.” With us, in similar circumstances, those taken in 
the evening were alive at noon on the following day. 
CHAP. IV.—ON MOLLUSCOUS ANIMALS AS OBJECTS OF 
UTILITY. 
Although molluscous bodies furnish many articles of value 
to man, scarcely any naturalist has taken the trouble to 
enumerate the different purposes to which they have been 
applied, or to point out in what manner their usefulness 
might be encreased. To the savage, shells furnish some 
of his most important instruments. They often answer all 
the purposes of a knife, and are extensively employed as a 
substitute for iron: with pieces of the more solid bivalves 
