T9I4-] N. Annandale : Fauna Symbiotica Indica. 155 



in figs. 2a and 3^7 on pi. x) in the structure of the extremities and 

 the size is a little greater, the average length being 0*0473 mm. 

 (extremes 0'043 and 0'05 16 mm.). Sigmata are very scarce ; they 

 are a little more contorted as a rule than those of M. aegagropila 

 from the same locality. Thetoxa, which are fairly abundant, are 

 extraordinarily variable in size: o'i4o to o'352 mm. in length. 

 Most of them fall into one of two series characterized by size. In 

 the smaller toxa the central curve is as a rule more compressed 

 than in the larger ones, which are actually longer than the 

 macroscleres. 



Type No. Z.E.V. "V^ Ind. Mus. 



Locality. — Madras harbour in 4 to 6 feet of water ; on living 

 shells of Mytilus latus, Lam. 



The degree of development reached by the skeleton in this 

 species is probably somewhat variable, but it is only in well- 

 preserved specimens on which no artificial pressure has been 

 exerted that the double system of spicule-fibres can be adequately 

 observed. 



Specimens of this species collected in October are full of 

 gemmules in early stages of development. Indeed, parts of the 

 sponge appear to consist of little else but morula-like masses of 

 cells evidently of this nature. 



Genus Lissodendoryx (Topsent) Lundbeck. 



Topsent, Mem. Soc. Zool. France \\\ p- 457 '^1897); Res. Camp. Sci. 

 Moiraco, fasc. II, p. 17,^ (1907); I.undbeck, Dan. 'Iiigolf -Exp. VI 

 (2), p. 153 (1905). 



Lissodendoryx balanophilus, sp. nov. 

 (Plates X, fig. 4 and xi, fig. 5.) 



The sponge forms a crust not more than 4 mm. thick on the 

 shells of Lamellibranchs, often occurring together with Balanus 

 amphitrite, Darwin. It fills up the interstices between individual 

 barnacles as well as growing over their shells in a thin film. The 

 external surface is irregular, but not spiny and without definite 

 projections. The colour is pale yellowish green and fades little 

 in spirit. The structure is somewhat cavernous owing to the 

 comparatively great calibre of the main exhalent channels, which 

 run obliquely upwards through the sponge and do not form branch- 

 ing grooves on the surface of the parenchyma. The oscula 

 are rather larger than those of the species of Mycale described 

 above, but the pores are minute and difficult to detect. The 

 whole sponge is very fragile, but rather less so than the others 

 found with it. 



The skeleton contains little binding substance. The dermal 

 macroscleres form short, somewhat plumose fibres in which as 

 many as 12 spicules abreast can sometimes be seen in optical 

 section. These fibres branch dichotomously or irregularly at 



