In a eukaryotic cell, the ribosomes are found in the nucleus but since a prokaryotic cell doesn't have a nucleus, the ribosomes are floating freely in the cytoplasm. Hope this helped :)
An endoskeleton made up of hard plates beneath the skin is a characteristic of the echinodermata phylum. Organisms under the phylum echinodermata have tight interlocking plates that form their endoskeleton. Sea urchins, starfishes and sea cucumbers are examples of echinoderms.