182 j. murray on water- bears, or tardigrada. 



Additional Genera. 



The genera to be described which were not noticed in the 

 earlier paper are four in number. Three of them have been 

 discovered since 1907; one was described before but was over- 

 looked for a long time. The new genera are Tetrahentron 

 Cuenot 1892 (2), Halechiiiiscus Richters 1908 (40), Batillipes 

 I^ichters 1909 (45), Oreella Murray 1910 (25). I shall not 

 attempt very full descriptions of these genera, as they are figured, 

 and a good picture conveys more than much writing. 



Genus Tetrakentron Cuenot (2) (PI. 8, Fig. 2). 



Resembling Echiniscus, but without plates. All the processes 

 on head and body are short palps or spicules, except one longer 

 hair on each side, at the base of the fourth pair of legs. The 

 head is truncate, and bears on its anterior margin three small 

 palps, one of them in the middle line. At the base of the head, 

 on each side, there is a short spine with a palp at its base, 

 corresponding to seta a of Echiniscus. There is a spicule at the 

 base of each leg. Each leg bears four equal and similar claws, 

 curved, widely separated from one another, and not borne on 

 papillae or " toes " as in Halechiiiiscus and Batillipes. The 

 figures show teeth, gullet and pharynx as in Echiniscus, and no 

 eyes. The body is dorso-ventrally flattened. Marine. 



The animal is parasitic on the holothurian Synapta. It is the 

 only instance of a parasitic water-bear known. It is easily 

 recognised from its peculiar habitat and the characters given. 

 While resembling Echiniscus, it has no plates, and the processes. 

 on the head are greatly reduced. The median palp on the front 

 of the head is not known in any other water-bear. 



Genus Halechiniscus Richters (40) (PI. 8, Pigs. 3a, 3Z*). 



Like Echiniscus, but without plates. The processes on the head 

 are well developed, but the palps near the mouth are lacking. 

 The seta a at the base of the head is thick, and the process at its 

 base, a palp in Echiniscus, is elongated both these processes 

 spring from a common papilla, as in Batillipes and Oreella. 

 The body bears lateral hairs, corresponding to c, d and e of 

 Echiniscus. The legs are jointed and telescopic, the last joint 

 very slender. Each leg bears four narrow toes, terminating in 

 short curved claws. 



