The class is divisible into two main divisions or sub-classes, Hydromedusae and Scyphomedusae, of which definitions and detailed systematic accounts will be found under these headings.
General Works on Hydrozoa.—C. Chun, “Coelenterata (Hohlthiere),” Bronn’s Klassen und Ordnungen des Thier-Reichs ii. 2 (1889 et seq.); Y. Delage, and E. Hérouard, Traité de zoologie concrète, ii. part 2, Les Coelentérés (1901); G. H. Fowler, “The Hydromedusae and Scyphomedusae” in E. R. Lankester’s Treatise on Zoology, ii. chapters iv. and v. (1900); S. J. Hickson, “Coelenterata and Ctenophora,” Cambridge Natural History, i. chapters x.-xv. (1906).
(E. A. M.)
[1] See further under [Scyphomedusae].
HYENA, a name applicable to all the representatives of the mammalian family Hyaenidae, a group of Carnivora (q.v.) allied to the civets. From all other large Carnivora except the African hunting-dog, hyenas are distinguished by having only four toes on each foot, and are further characterized by the length of the fore-legs as compared with the hind pair, the non-retractile claws, and the enormous strength of the jaws and teeth, which enables them to break the hardest bones and to retain what they have seized with unrelaxing grip.
| Fig. 1.—The Striped Hyena (Hyaena striata). |
| Fig. 2.—The Spotted Hyena (Hyaena crocuta). |