420 
ZOOLOGY OF THE FAR EAST. 
fusion of the sixth and seventh joints. A careful comparison and measurements of 
his figure show that in his specimen the second and third joints were not fused and 
that the explanation of the reduction in the number of joints is reall}^ due to the 
fusion of the sixth and seventh. 7". spongillicola therefore is not in agreement with 
the generic diagnosis of Tachaea in this respect. 
Thielemann describes and figures the maxillipedes of T. chinensis as five-jointed, 
and it is evident that, in this case, the second and third, and sixth and seventh 
joints are fused. 
T. chinensis would then appear to combine the characters of T. crassipes and 
T- spongillicola as far as the maxillipedes are concerned. But these appendages are 
very small and delicate and the joints very difficult to make out and the condition 
which I have noticed in these Chinese and Japanese specimens may possibly explain 
the apparent differences in the three species. On the elongate second joint there are 
traces, visible at the sides, of a suture, but it is not continued across the joint. I take 
it that this represents a partial separation of the second and third joints and a 
similar incomplete suture is visible on the terminal joint indicating the partial 
separation of the sixth and seventh joints (PI. XVI, fig. i8). 
But in neither case could I trace the suture right across the joints, and I should 
describe the maxillipedes as five- join ted with partial separation of the second and 
last joints into two. It looks to me as if Stebbing saw a similar partial suture 
between the second and third joints, but not between the sixth and seventh joints in 
his species, while Thielemann does not mention either. My point is that the 
apparent differences in the descriptions and figures of the maxillipedes of the three 
species are not nearly so important as they seem at first and may be explained by the 
delicacy of the appendages and the difficulties of seeing the sutures. 
There are three species of Tachaea known from fresh water, T. lacustris, Weber, 
from Sumatra, T. spongillicola from Calcutta, and T. chinensis from China and Japan. 
These three species are very closely related to one another and structurally there 
seems very little to distinguish them. But each has a very distinct habit. T. lacustris 
was found on Cyprinoid fishes, T. spongillicola in the canals of a freshwater sponge 
and the present specimens of T . chinensis, both from China and Japan, were found 
clinging to the carapaces of various freshwater Macrura, Caridina, Palaemonetes 
and Leander. 
Thielemann's type specimens were obtained in the market at Shanghai, so the 
present collection provides the first indication of its habit and mode of life. I could 
not detect any differences between the Chinese and Japanese specimens. Both are 
characterised by a profuse development of black arborescent chromatophores on 
the body and the appendages. 
"All my specimens were from pure fresh water, and were associated with small 
prawns of various genera. The common Indian species {T. spongillicola, Stebbing) is 
also found adhering to the external surface of the carapace of small freshwater prawns, 
especially when young, as well as in the canals of Spongilla. In neither species is the 
association of a permanent nature. N. A." 
