Mysidacea, Tanaidacea and Isopoda. 
419 
This new form removes one more of the characters separating the genus 
Caecidothea from Ascllns, the presence of eyes in the latter and their absence in the 
former. There remains only the general form of the body and the size of the head 
and pleon to separate the two, and among the known species of Asellus and Caecidothea 
there are all grades of shape, which would make a continuous series of connecting 
forms. The validity of the genus Caecidothea is indeed doubtful. 
This species is a most interesting addition to the fauna of Japan. Its nearest 
allies are all American species, found in subterranean caves and springs in Kentucky, 
Tennessee, Texas and so on. 
Sub-order FLABELLIFERA . 
Fam. CYMOTHOIDAE. 
Genus Tachaea, Sch. et Mein. 
Tachaea chinensis, Thielemann. 
(PI. XVI, figs. 16-18.) 
T. chinensis, Thielemann, 1910,. p. 18. text figs.. 12-20. 
Localities : — 
China. 
N.E. end of Tai Hu, near Moo Too, China, i. xii. 15, 2 females, 7 mm. 
Outskirts of Shanghai, in ditches and ponds, adhering to the carapace of 
Caridina nilotica subsp. gracilipes and Palaemonetes sinensis, 3 immature, 3-4'5 mm. 
Japan. 
Ogura Pond, near Kyoto, from Leander paucidens, 6 specimens, 6-9 mm. Lake 
Kasumi-ga-Ura, on the east coast 15. x. 15, from the carapace of Leander paucidens, 
sixteen, 6-9 mm. 
These specimens, both from China and Japan, differ from the description and 
figures given by Thielemann in two particulars, (i) there is a distinct lacinia mobilis 
on the mandible (PI. XVI, fig. 16), tipped by two or three small setae (ii) the single 
strong curved spine on the first maxilla (PI. XVI, fig. 17) is longer than Thielemann 
shows and more like that figured by Stebbing for T. spongillicola. 
These small differences bring T. chinensis much more closely in agreement with 
T . spongillicola and I am inclined to doubt whether they are really separate species. 
But I have not seen specimens of Stebbing' s species and the question cannot be 
decided until specimens are compared from both localities. 
Hansen (1890) in his monograph on this and allied genera, figures a six-jointed 
maxillipede for the type species T. crassipes and states in the diagnosis of the genus 
that the second and third joints are fused, thus accounting for the reduction in 
number of the joints of the appendage from seven to six. 
Stebbing (1907) in describing T. spongillicola, says that the maxillipedes are 
decidedly only six-jointed and he explains the reduction in this species as due to the 
