102 Records of the Indian Museum. [Voi,. TIT, 



Habitat. — Backwater ' near Shasthancottah, Travancore, in 

 slightly brackish water ; on the roots of shriil)s growing at the edge ; 

 November, 1908. 



This species is easily distingnished from its allies of the sub- 

 genus I-'uspoiigi/la, all of which are closely related, by its adherent 

 gemmules with their (usually) multi])le a]iertures and rough external 

 surface. 



Genus TruKiXA. 



Tuhclla pcnnsylvaiiica , Potts. 



Potts, Proc. Acad. Nat. Set. Philadelphia, 1887. p. 251. 

 plate xii. 



By the kindness of the authorities of the Smithsonian Insti- 

 tution I have been able to obtain jiieces of the freshwater sponges 

 in the collection of the United States National Museum. As the 

 majority of these were named by Potts, the acquisition is an ex- 

 tremely valuable one. It enables me to identify with certainty 

 several Indian species with American forms, amongst others the 

 one of which the name is printed above, viz., Tuhella pennsylvanica. 

 This species, found by Potts in Pennsylvania, New Jersey and 

 other parts of the Eastern United States, was afterwards re- 

 ported from the west of Ireland by Hanitsch {Irish Naturalist, iv, 

 p. 129, 1895) and from the Inner Hebrides of Scotland by myself 

 Ijourn. Linn. Soc, xxx, p. 248, 1908). None of the European 

 specimens as yet discovered, however, have contained gemmules, 

 and their identification has therefore remained a little doubtful. 

 Specimens recently collected in Travancore are full of gemmules 

 and agree more closely in every respect with one of the American 

 specimens examined than this specimen does with a second one 

 from the United States. They have the somewhat slender pointed 

 skeleton spicules and markedly unequal rotules of the gemmule 

 spicules of the typical form of the species. Indeed, the American 

 specimen which they resemble so closely is apparently part of the 

 same specimen as that of which the spicules are figured by Potts 

 in fig. I of plate xii of his monograph. 



The measurements of the spicules of an Indian specimen and 

 of one from lychigh Gap, Pennsylvania, are given for comparison : — 



Travancore. Pennsylvania, 

 lycngth of skeleton .spicule . . 0189 — 0-242 mm. ot6 — 0-21 mm. 



(average 0203 mm ) (average 0-195 mm.) 

 Breadth ,, ,, ,, .. 0-0084 — 001 55 mm. 0*0084 ram. 



Ivcngth of birotulate .. .. 0-0126 mm. 0-0099 >. 



Diameter of upper rotule .. 00084 .. 00084 ,, 



,, lower ., .. 00189 ,, 0-0168 ,, 



,, gcmmiile .. .. 0-243 — 0-348 mm. 0-174 — 0-435 mm. 



' The backwaters of Cochin and Travanonn^ are a series of lagoons directly 

 connected at intervals with tlie sea, from whicli they are separated by a more or 

 less narrow extent of land. Tl.ey have been artificially joined togetlier by canals 

 and receive a good deal of fresh water. Their salinity varies with the place and 

 the season. 



