214 MOLLUSCA. 
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, Leachit 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 Evca@71um.—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 F. hospitiolum of Sav. tab. iv. f. 4., is 
the only known species. 
2. Tribe. 
Body free, and moving about in the water. 
Genus Prrosoma.—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, 
with a membranaceous ring at the entry. The branchie 
are disjoined. The abdomen is inferior to the branchie, 
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, 
