630 
RADIATA. 
THE COMATULID^. 
This family, the species of wMcli are called Hair-Stars or Feather- S tar includes a con- 
siderable number of animals, wbicli bear 
a great resemblance, both in form and 
structure, to the Encrinidse. They are, 
however, only furnished with a stalk dur- 
ing their young state, and on arriving at 
maturity they quit their attachment, and 
crawl about freely at the bottom of the 
water, in the same manner as other star- 
fishes. The body is flattened and cov- 
ered with separate calcareous plates ; the 
lower, or ventral surface, bears the mouth 
and anus; and the ten slender rays are 
often branched to such an extent as to 
appear very numerous. These are fur- 
nished throughout their length with slen- 
der, jointed cirri, similar to those of the 
Encrinidse, by the assistance of which and 
the short ambulacra, the Hair-Stars are 
enabled to grasp any object firmly, and 
creep about on submarine plants with 
great ease. 
In their young state, the Comatulce 
greatly resemble the animals of the pre- 
ceding family, being supported on a long- 
flexible stalk, formed of calcareous cylin- 
ders. So close is this resemblance, that 
when first discovered the young of the 
Comatula was described as a Pentacri- 
nus. These animals are tolerably numer- 
ous in the seas of the present day, where 
they constitute, in fact, the principal 
representatives of their order. In the 
earliest ages of the world, their place 
was taken by the fixed Encrinida? ; and the free Comatulse do not make thfeir appearance in any 
formation earlier than the Jurassic strata. 
THE MEDUSA S HEAD PENTACEINUS. 
Class II. SIPHOWOPHOMA. 
The Svphonophora form a group of animals of which we have still much to learn before their 
true nature and relations can be ascertained. They are divided into two orders — the Physograda 
and Chondrorjradci. 
ORDER 1. PHYSOGEADA. 
The characteristic of the animals forming this order is, that they are furnished with a vesicular 
organ containing air, which serves as a float to buoy them up in the water. The best known 
of this species is the Physalia Atlaniica, which has received from sailors the name of the 
Portuguese Man-of- War. It swims in great crowds at the surface of tke water, and possesses a 
very strong urticating or stinging power. 
