I ^0 ] 
The Tetrabranchia have four gills, an external shell, 
numerous fentacles and a funnel consisting of two halves. 
They have no ink bag. There are only four living forms repre- 
senting this group and alt belong to thf* jjenus Nauiilus, but 
several th lusand extinct species are kn-j.vn. AH the fossil 
Ammonites belonged to the same group. Some of them had coiled 
shells, like Nautilus, others straight ones, which have to be 
understood as having become unrolled. Some of those straight 
forms, like Endoceras and Orihoceras, used to reach a length 
of six feet, whilst some of the coiled Atmmnites grew to over 
two feet in diameter. The shell of Nautihis is chambered, the 
animal inhabiting only the last corapartmentp but all the vari- 
ous chambers are connected with each other by holes in the 
septa. 
The Dibranchia have two gills, a rudimentary internal 
shell, eight or ten arms, a funnel consisting of one piece only, 
and an ink bag. All their arms bear rows of suckers which in 
the largest species attain the size of a saucer. They are further 
divided into Deaipodit, with ten arms, and Octopoda, with eight 
arms. 
The Decapoda * have ten arms two of which are much 
longer than the eight others. Their body is generally elongated 
and provided with lateral fins. This section includes, besides 
the fossil Belcmnites, Spinda (see p. 89), the true Cuttle-fish 
{Sepia), the smaller Sepioia. and the Scjuid {LQligo), Sepia has 
a catcareous internal shell, but Loiigo a horny one, in the shape 
of a spear head. The largest Cephalopods observed yet belong 
to the genus Architeuthis and are allied to the Squids. A mon- 
ster was caught off Newfoundland, in 1874, the two long arms of 
which measured 24 feet each, and the eight short ones 6 feet 
each.. 
The Octopodti have eight uniform arms and a short rounded 
body, Oct&pus and the Paper-Nautilus {Arganauta argo) belong 
to this group. 
Cuttle-fishes of all sorts form an important and much 
esteemed article of food amongst the Chinese. They are light- 
ly salted, pressed and sun dried, and Tenison Woods says that 
*' al! kinds are eaten," but that " the best one is the little 
Sepi&la which is really a dainty morsel when properly cooked/' 
* It is unfortunate that Ihe term 'Decapoda' it al&o ut«d for ta order of the 
Crustacta {see p- / iK The l«o gmups have nothing in comfnan. 
