290 M. Krohn on the Anatomy and 
almost regularly fusiform, growing narrow at its two extremities, 
but particularly at its posterior extremity. At the anterior ex- 
tremity of the body a head is readily perceptible. Five pro- 
jecting appendages then strike the eye of the observer, extended 
horizontally, and placed on the posterior half of the body: 
these appendages have the form of leaflets or fins, and give 
the animal, at first sight, some resemblance to a fish*. They 
are attached to the body by a widened base, and diminish gra- 
dually in thickness up to their margin, where they are very 
soft and flexible. The hindmost of these fins, that which em- 
braces the posterior extremity of the body, is an odd one: the 
four others are arranged in pairs, that is to say, one opposite 
another, on each side of the body. The posterior fin is triangular, 
similar to the caudal fin of a fish, or rather, on account of its 
horizontal position, comparable to the terminal fin of the Cetacea. 
Kach leaflet of the anterior pair of fins, placed almost in the 
middle of the body, has the form of a segment of a circle, whilst 
the two laminz which constitute the following pair, longer and 
wider than the lamine of the first pair, resemble, up to a certam 
point, a segment of a rhomb. 
The head is manifestly isolated from the body, and surrounded 
by a kind of membranous hood, which the animal can draw 
back, and which it does in fact draw back when it seizes its prey. 
The upper surface of the head is placed on a level with the upper 
plane of the body ; its lower surface, on the contrary, is oblique 
from above downwards and from before backwards. When the 
hood is in the state of the most complete expansion and brought 
over the head, the latter is entirely enveloped in it, with the ex- 
ception of its under surface, in the middle of which is seen the 
mouth in the form of an elongated depression. When the animal 
draws back this hood, the head, and particularly its sides, are ex- 
posed, and the parts which I proceed to describe are perceived. 
In front and on each side there is a simple row of horny hooked 
prickles, arranged in a curved line, directed obliquely from above 
downwards and from before backwards (these are the palpes striés 
of MM. Quoy and Gaimard) ; they enable the animal to seize 
and bruise its prey. Their number varies in different indi- 
viduals from five to seven on each side. They differ from one 
another in size; the upper or anterior hooks bemg most fre- 
quently shorter than the lower or posterior ones, which in their 
turn are shorter than the three or five middle hooks. They 
are very much flattened, but present a decided curve and a 
pointed end. The base by which they are attached to the skin 
* For this reason the fishermen of Messina call this animal Spadella,— 
the diminutive of spada, a sword. 
