CE'RAPUS, a genus of Amphipodous Crustaceans forming the sixth division of the third section of the order Amphipoda (Latreille), according to Desmarest. The following are the characters of this division :—All four antennte very great and strong, and nearly of the same length; the upper with four joints, the lower or lateral ones with five.
Say first established this genus, which has the antennae hairy, and performing iu some sort the office of limbs, herein corresponding in a degree to the lower antenna: of the Corophia of Latreille. Feet of the first pair small, and terminated by a simple short nail ; those of the second pair on the contrary very large, having a large, flat, trian gular manus provided with a biarticulated thumb, corresponding to'a well-developed point which represents the immoveable finger in the ordinary crustaceans; those of the three succeeding pairs moderate and monodaetylous, and the four last longer, more slender, and directed backwards and upwards. Bodylong, linear, demicylindrical,
composed of twelve segments, the last of which is flattened into the form of an oval plate furnished on each side with a small bifurcated appendage at the extremity. Head terminated by a very small rostrum. Eyes projecting.
Example, Cerapus tubularis. Like the larvae of the Phryganem this extraordinary crustacean, which is about six lines in lerigth, lives in small cylindrical tube, which is considered to be that of a Tubularia, exposing only the head, the four large antennte, and the two first pairs of feet. The species occurs in abundance in the sea near Egg Harbour in the United States, in the midst of Sertularim, which are supposed to form its principal food. (Journal of the Academy of Nat. Sea. of Philadelphia, voL i. p. 49, pl. 4.)