9 
of Spirilla australis, Lamarck. 
(PI. I. fig. 3, a c) are disposed in regular fasciculi; they are 
not transversely striate. 
The tongue has a single retractor (PI. I. fig. 8, t : the mus¬ 
cles of the mandibles, r, s , are shown in this figure). 
The brain is immediately covered by delicate meninges; and 
the part of the cartilaginous cranium protecting its periphery 
is thin. It presented a small anterior u cerebral ” or olfactory 
lobe (PL II. fig. 2, a) set upon the large optic lobes ( b ), like 
the crystalline lens upon the vitreous humour. 
The pallial nerve-trunks (c) perforate the u retractores 
infundibuli,” and swell into the “ ganglia pallialia ” ( d ). 
The visceral nerves (e) descend together, dorsad of the 
oesophagus, between the inferior salivary glands, and, with 
the oesophagus, enter the interspace between the hepatic lobes. 
They send filaments to the salivary glands as they pass be¬ 
tween those glands; and continuing backward and ventrad 
between the hepatic lobes to the gastric ganglion, they send 
filaments to the “ hemispheric mass” ( z ) in the last shell- 
chamber (m). 
Dorsad of the infundibulum project the two large subspheri- 
cal ear-capsules (PI. II. fig. 6, a), the soft subtransparent 
walls of which permit the contained opaque white otocones ( b ) 
to be discerned. The cartilage of the auditive capsule pre¬ 
sented a bluish hyaline colour ; that of the orbits was of a 
grey colour and more opaque. 
Immediately in advance of the acoustic capsules the car¬ 
tilaginous orbital cup of the cranium extends forward, ex¬ 
panding. A thin sheath or layer of muscular fibres arises 
from the ventral side of the skull to pass upon the liver: in 
advance of this a fibrous layer is directly continued from the 
margin of the cartilaginous orbit upon the sclerotic. The 
pupillary aperture (PI. I. fig. 4, a) is subcircular and opens 
into the extensive conjunctival or aqueous chamber (PI. II. 
fig. 2, l), which extends on one side of the eyeball to near the 
large optic ganglion if). 
The conjunctive membrane is reflected from the postorbital 
cavity upon the side of the gullet and base of the circular 
eyelid ; it is connected with the sclerotic ( l ) by loose laminated 
cellular tissue, together with granular adipose tissue and the 
great optic ganglion. 
The precranial part of the gullet (PI. II. fig. 2, k ; PI. I. 
figs. 8, 9, k) is 5 millims. in length; the tube then enters 
the canal or groove in the cartilaginous skull; and the brain- 
membrane is reflected upon the oesophagus as this tube (PI. I. 
fig. 11, a) with the salivary ducts (b) passes through the 
cerebral ring. 
Three filaments accompany the cephalic part of the oesopha¬ 
gus : the middle and broadest (b) is continued from the ventral 
