110 J. MURRAY 



NOTES ON THE SPECIES 



Genus Echiniscus, Schultze 



A : SPECIES HAVING SEGMENTS V. AND VI. DISTINCT 

 Echiniscus mutabilis, Murray 



The commonest Echiniscus in New Zealand, occurring in many localities in both 

 of the large islands, but not in Stewart Island, the Aucklands, or the Macquaries. 



I was formerly inclined, relying on second-hand descriptions of E. arctomys, 

 Ehr., to believe that E. mutabilis was closely related to that species. Reference to 

 Ehrenberg's original figure (4) and description (3) shows that they have nothing in 

 common. They even belong to different sections of the genus, which will probably 

 become distinct genera eventually. E. arctomys has segments V. and VI. (Richters) 

 completely fused, and E. mutabilis has these segments distinct. Any records which 

 I have made of E. arctomys in previous papers are erroneous they all refer to 

 E. mutabilis (see p. 126, footnote). 



Echiniscus novwzeelandice, Richters (37) (Plate XV. Fig. 5) 



Specific characters. Segments V. and VI. separate, V. a pair, obscurely divided, 

 bearing two stout dorsal processes somewhat near the median line : first and second 

 median plates divided by transverse line : all finely dotted : no fringe on the 

 fourth legs. 



Description. Professor Richters contents himself with a rather brief diagnosis, so 

 a fuller one is given here. The animal varies considerably, in size and other respects. 

 It is the closest relative of E. mutabilis, and it is doubtful if they could be 

 distinguished, except by the characteristic spines on V. The colour varies from 

 brick-red to yellow. The number of plates is difficult to state, on account of the 

 obscure separation of some of them, and the sub-division of others. I prefer to 

 regard those sub-divisions as not constituting distinct plates, and thus consider a 

 typical animal in which V. and VI. are distinct as having twelve plates, of which 

 three are median, and there are three pairs. There are species in which the plates 

 of the third pair (segment V.) are completely fused. 



Apart from the ten processes on the head, which appear to be common to all 

 Echinisci* there are usually no processes on the body of E. nonezeelandice except 

 the two stout spines on V. These vary greatly in size, sometimes reaching almost 

 as far as the posterior border of plate VI., sometimes reduced to short cones. In 

 one example they measured 30 n in length. 



These processes are often forked. There are often short cones at the postero- 

 lateral margins of the plates of the second pair (d Richters). There may be rudi- 



* Except only E. ImberUs, which is said by Prof, Richters (38) to lack the six processes near the mouth 



