516 Transactions of the Society. 



Fourteen species have been found, belonging to the three genera, 

 Echiniscus, Milncsium, and Macrohiotus. 



There are eight species of Echiniscus, and five of Macrohiotus ; 

 of Milnesium there is only one well established species known. 



It is remarkable that eight out of the fourteen species are 

 distinct from any species previously known. The only known 

 species of Echiniscus found is E. arctomys ; the known species of 

 Macrohiotus are M. echinogenitus Eichters, and M. hufelandii 

 Eichters ; M. arcticus is a doubtful identification ; Milnesium tardi- 

 gradum is of world-wide distribution. 



Two of the species of Echiniscus were not sufficiently studied 

 to justify me in naming them, but they are figured and described. 



List' of Species. 



Echiniscus arctomys Ehr. 



„ - hispinosus sp. n. 



„ africanus sp. n. 



„ ^jer«?'?na/'2is sp. n. 



„ longi&pinosus sp. n. 



„ crassispinosus sp. n. 



sp. (?) . 

 . ,, . sp. (?)• 

 Milnesium tardigradum Doy. 

 McLcrohiotus hufelandii Eichters. 



„ echinogenitus Eichters. 



„ arcticus Murray (?). 



„ nodos7is sp. n. 



„ crassidens sp. n. 



Echiniscus. 



There are two well-marked groups within the genus. The first 

 has segments v. and vi., as defined by Eichters (8)* quite distinct. 

 Segment v. is either a half-ring or forms a third pair of plates. 

 Two African species belong to this group, E. arctomys and E. bi- 

 sinnosus, and both have segment v. as a half-ring. 



The second group has segments v. and vi. completely united, 

 so that the junction cannot be distinguished. The common plate 

 thus formed is rendered trilobate by two lateral clefts, in the same 

 way as plate vi. of the first group. This group includes six of the 

 African species, and the great majority of known species. 



In the descriptions of species of Echiniscus the body is regarded, 

 following Professor Eichters (<S'), as consisting of six segments, 

 which are distinguished by Eoman numerals i.-vi. These numbers 

 correspond with names I have used for the various plates, as 



*, Th,e figures in brackets refer to the list of literature at end of paper. 



