of Spirula australis, Lamarck. 11 
ing muscular part are “smooth” and disposed in longitudi¬ 
nal bands. 
The lower ends of the liver-lobes, or continuations of their 
capsules, enter the last chamber of the shell, and contribute 
to form the hemispheric mass (PL II. fig. 4, 2 ), from the cap¬ 
sule of which the membranous siphon (ib. v'j is continued. 
The outer cellular membrane, or covering of the liver, is 
condensed where it connects the lobes with the u hemispheric 
mass,” and forms a well-defined border of the part occupying 
the last shell-chamber. 
The liver consists of well-defined pyriform sacculi ; the 
obtuse round blind ends, being next the capsule, give the 
reticulate appearance (PI. II. fig. 4, l). 
The last chamber of the shell is filled by a solid, soft, 
hemispheric body, covered by delicate smooth membrane, from 
which the small siphuncle (ib. v) is continued. The dissec¬ 
tion made with the view of determining the nature and con¬ 
nexions of this membrane is represented in figure 4, PI. II., 
the shell being removed. 
The shell-membrane, continued from the fibrous sheath 
formed by the origins of the retractores capitis et infundibuli, 
divides into two layers, one of which (v!) is continued over 
the exterior of the shell and is lost in the periostracum; the 
other lines the last chamber, coating its contents ( 2 ), and is 
continued therefrom to form the membranous siphon ( v ') ; 
from this a third thin layer extends from near the basal cir¬ 
cumference of the hemispheric body ( 2 I upon the “capsula 
propria” of the liver. This being removed, the structure of 
the hepatic gland is indicated by an irregular subhexagonal 
pattern of the surface. A circular indent of the shell-mem¬ 
brane marks the terminal margin of the calcified part of the 
last chamber. In the siphon fine muscular fibres could be 
traced the whole length. 
The calcareous siphon (PI. II. fig. 2, v ) slightly diminishes 
as it passes backward, and is surrounded by a raised border 
where it enters the aperture in the next septum. 
The anterior aorta passes to the interspace of the u retrac¬ 
tores capitis,” and goes forward alongside the oesophagus. 
Dorsad of this aorta the vena cava (PI. III. fig. 3, e) enters 
the same fissure and receives the hepatic vein, vdiich emerges 
between the cystic follicles and the duodenum. It then pene¬ 
trates the urocardial chamber, divides, and develops the renal 
follicles (c?, d). 
Each branchial heart (PI. III. fig. 3, b, b) is semicircular, 
subcompressed, with a small spherical appendage (c) ; it re¬ 
ceives the large vein with w hich the renal (?) spongy appen¬ 
dages are connected. These follicles contained small coagu¬ 
lated masses, consisting of filamentary groups ot cells, bent 
