REPORT ON THE TETRACTINELLIDA. 
43 
II. Microscleres. 4. Sigmaspire, 0’0125 mm. long. 5. Spherule, 0’0042 mm. in 
diameter. 
Colour. — Grey. 
Habitat. — South-east coast of Arabia. 
Remarks. — Carter’s description leaves little doubt as to the genus to which this sponge 
must be assigned, since he speaks of the cortex as “ loose and ill-defined, with tufts of 
spicules matted together with dermal sarcode.” There are but a few dried fragments of 
the sponge in the British Museum collection, and so far as the structure of the ectosome 
could be made out in these, it appeared to be that of Tetilla. 
Tetilla (?) australiensis (Carter). 
Tethya cranium, var. australiensis. Carter, Ann. and Mag. Nat. Hist., ser. 5, vol. xvii. p. 127, 
1886. 
Sponge ellipsoidal, sessile (?), surface finely hispid ; oscules numerous, small ; pores 
generally distributed. 
Spicules. — I. Megascleres. 1. Oxea, fusiform, finely pointed, 5 ‘7 by 0’038 mm. 2. 
Protrisene nearly the same length as the oxea; cladi 0T35 mm. long. 
II. Microscleres. 3. Microxea, minutely spined, 0’21 mm. long. 4. Sigmaspire, 
0’017 mm. long. 
Colour. — Yellow. Size 112 mm. high, 65 mm. wide, and 37 mm. broad. 
Habitat . — Port Phillip Heads, South Australia ; depth, 20 fathoms. 
Remarks. — This species is distinguished not only by the oxeate microscleres but 
also by the large size of the sigmaspire. The oxeate microscleres are almost unique 
among the Tetillidae, Tetilla merguiensis being the only other species possessing them, 
and in it they are nothing like so abundant as in the present species. 
Tetilla casula (Carter). 
Tethya casula. Carter, Ann. and Mag. Nat. Hist., ser. 4, vol. viii. p. 99, pi. iv. figs. 1-9, 1871. 
Sponge, see Carter’s description [loc. cit.), distinguished by its remarkable basal 
fringe of spicules. 
Spicules. — I. Megascleres. 1. Oxea, fusiform, 5'0 by 0‘045 mm. 2. Protrisene, 
rhabdome 10*42 by 0*013 mm., cladome distinguished by its short cladi, 0*039 mm. 
long, chord 0*026 mm. 3. Trichodal protrisene, marginal to the pore-areas, 0*416 mm. 
long. 4. Anatrisene absent. 
II. Microsclere. 5. Sigmaspire, 0*014 mm. long. 
Habitat. — Port Elizabeth, Natal, South Africa (Carter). 
