226 ASPIDOBRANCHIA. CHITONIDZ. 
Branchie \amellarum minimarum triangularium composite ; 
ad latera sua venee branchiales principales locantur. 
Cerebrum inter oris massam carnosam et oris velum locatur ; 
aspectus suus anterior a velo nervorum ramulos plurimos 
recipit ; ganglia duo, utrinque nervos duos emittentes, circuli 
nervosi partem anteriorem formant; ganglia duo posteriora 
nervos tres recipiunt, et ramo intermedio jungentes circuli ner- 
vosi partem posteriorem formant: gangliorum rami posteriores 
probabilitér ex visceris et pedis musculis exsurgunt. 
The shell is composed of eight arched lamelle covering the 
back*. 
The animal with its head jomed to the body by its mantle ; 
the mouth furnished with a fleshy lip and spiny tongue; has 
no jaws, but has in the situation of the upper jaw a cartilagi- 
nous lamella. 
The mouth of the animal is rostriform, short, retractile and 
fleshy ; lip without jaws, and a spiny tongue, with a peculiar 
sac at its base: the cesophagus is short, dilated into a stomach 
whose inner surface has elevated ridges; the intestinal canal is 
very long, very slender, and very often replicated ; the liver is 
very large with many lobes divided into many smaller lobes 
resembling little trees: between these lobes are placed the sto- 
mach and the reflections of the intestine. 
The pericardium is situated between the oviduct and the pos- 
terior margin of the cavity containing the viscera: the heart is 
symmetrical, consisting of two ventricles and two auricles ; the 
ventricles each of them has two very distinct orifices with the 
auricles, which have two similar orifices. Out of the heart 
anteriorly passes out the branchial artery, which, after supply- 
ing the branchiz (gills) with blood, terminates at the head 
with many minute branches: the branchial artery receives the 
blood from the lateral veins and distributes the blood to the 
liver and the intestines. 
The branchiz are composed of small triangular lamelle ; on 
their sides the principal branchial veins are situated. 
The brain is situated between the fleshy mass of the mouth 
* Accidental varieties have seven or six valves, which have been consi- 
dered as distinct species. 
