FRESHWATER ISOPOD FROM CALCUTTA. 41 



longer, the fourth joint especially gaining in lengih, the fifth Jistally fringed 

 with numerous spines. 



The second pleopods of the male have the masculine appendix produced 

 almost to a point much beyond the smooth inner plate and the broader and 

 longer outer plate, which is fringed nearly all round with short plumose seta?. 



The uropods have the inner angle of the peduncle well produced, apically 

 armed with two setae; the large inner ramus fringed with setse and spines, 

 distally truncate with oblique corners ; the much narrower outer ramus 

 similarly furnished, a little shorter, with apex obliquely truncate. 



The specimens as preserved retain dark stellate markings distributed over 

 the back in a roughly symmetrical pattern, the central group broad with 

 occasional bare spaces, the marginal groups very irregular, and between these 

 and the central group two narrow snbmedian lines. 



The female specimen was 9 mm. long by 4-5 mm. broad; the male 5-75 mm. 

 ]x)ng by 2" 7 5 mm. broad. 



Locality. — Freshwater tank, Calcutta. Dr. Annandale found the specimens 

 described, and a third smaller than either, in the canals of a freshwater 

 sponge, SpongiUa carteri, Bowerbank *, and to this choice of residence the 

 specific name refers. 



The hitherto known species of this genus are Tachcea cr'assijjes, Schiodte 

 & Meinert, from coral-reefs at Singapore, and Taclicpa incerta, H. J. Hansen, 

 of unknown locality. The latter author re-examined, and gave fresh fionres 

 and description of, T. crassipes, which he sup})osed to be founded on youno- 

 specimens, probably of the female sex. His own species was founded on 

 a female specimen, a very old and unfortunately a defective one. It was 

 light brown in colour without dark blotches, but Hansen was uncertain whether 

 that might not be due to the bad state of preservation. It appears to be 

 distinguished from T. crassipes chiefly by a slenderer sixth joint in the first 

 three thoracic limbs, and by having the telson distally rounded instead of 

 truncate. In the freshwater species here described it is the male that has 

 the slenderer limbs, but in the shape of the telson this sex agrees with 

 T. crasfipes, while the female in that respect agrees with T. incer'ta. Hence 

 I am disposed to infer that T. incet'ta is not distinct from 2\ crassipes, and 

 that T. spongillicola is a very near relation to the same species, distinguished 

 chiefly by the terminal joint of the maxillipeds, but apparently also by having 

 the limbs somewhat less spiny and the pleon shorter in comparison with the 

 pergeon. At some future opportunity it would be interesting to test by 

 experiment whether the freshwater form could support life in sea-water. 



* According to later information, the sponge may be a local race of Spoitgilla lacustrcs 

 (Donati). 



LINX. JOURN. — ZOOLOGY, VOL. XXX. 4 



