This is the con: verse of the preceding form. The two bodies are united below, and diverge from one another so that the heads are at the opposite poles. The two pelves are united, and sometimes the two sacra have coalesced in such a way that the spinal canals are continuous. All the organs of the chest and abdomen are doubled, but one set of the external sexual organs may be imperfectly formed or may have coalesced with the other. There are generally four legs, which are thrown to the .sides, but there may be three or only two.