The second order of the Eucarida, the DECAPODA, is by far the largest of the orders of Crustacea, and it includes all the larger and more familiar members of the class. It is necessary, therefore, to give a considerably fuller account of its subdivisions than has been given in the case of the other orders. The typical characters of the Decapoda are well illustrated by the Lobster, which has been already described. As in the Euphausiacea, the eyes are stalked, and the carapace fuses with all the thoracic somites. From the Euphausiacea the Decapoda differ in the fact that three pairs of the thoracic limbs are modified as maxillipeds, the remaining five pairs forming the "ten legs" to which the name of the order alludes. Further, the gills are arranged in more than one series, not all attached to the bases of the legs, as in the Euphausiacea, and covered over by the side-flaps of the carapace instead of being freely exposed. While agreeing in these essential characters, however, the members of the order Decapoda differ very widely among themselves in structure and in general form, and they are classified (in the arrangement adopted here) in two suborders, which are again subdivided into sections and tribes. ORDER DECAPODA. Suborder NATANTIA - { Tribe Penæidea. { " Stenopidea. { " Caridea. " REPTANTIA. Section _Palinura_ - { " Scyllaridea. { " Eryonidea. " _Astacura_ - " Nephropsidea. " _Anomura_ - { " Galatheidea. { " Thalassinidea. { " Paguridea. { " Hippidea. " _Brachyura_ - { " Dromiacea. { " Oxystomata. { " Brachygnatha. Subtribe Brachyrhyncha. " Oxyrhyncha.