REPORT ON THE TETRACTINELLIDA. 
39 
report^ on the Rev. Dr. Norman’s Norwegian Sponges. It difiers in the characters of its 
spicules ; the sigmaspires are considerably larger (as 5:3), and the anatrisenes and protriaenes 
differ from those of Craniella cranium both in form and size, the cladi of the anatrisenes 
make a larger angle with the rhabdome, and the cladi of the protrisenes are both thicker and 
more widely divergent. The cortex is 0’4 mm. thick. Oscar Schmidt has described two 
sponges, one from Iceland and the other from Florida, both as the species Craniella cranium. 
From an examination of the spicules mounted from these, and presented by Dr. Schmidt 
to the British Museum, I am led to doubt whether either of them is rightly assigned. 
The one from Iceland does not appear even to belong to the genus, and is probably a 
Tetilla. Its spicules include an oxea, 3 ‘5 5 mm. long, two kinds of protrisenes, one with 
stout equal cladi, and the other with one cladus longer than the other two ; the rhabdome 
of this is 1‘67 mm. long, the longer cladus 0T06 and the two shorter cladi 0’035 mm. 
long. The anatrisenes are broken, so that their length cannot be ascertained ; the dia- 
meter of the rhabdome is O'Oll mm., the cladi measure OTOl by 0*009 mm., and the 
chord is 0'07 mm.; the sigmaspire is 0'019 mm. long. 
The spicules of the specimen from Florida, also named Craniella cranium, are very 
different from those of the preceding, and probably come from a species of Craniella 
(probably Craniella carteri). The large oxea measures 4*26 by 0*044 mm., the sigma- 
spire 0*014 mm. 
Craniella sclimidtii (f). 
There are two other small specimens (4 to 5 mm. in diameter) in the collection, 
which, so far as regards their spicules are almost identical with Craniella schmidtii. 
They differ, however, from this species and from the genus in the structure of the cortex, 
which is not differentiated into an outer and an inner layer as in Craniella, but consists 
of a single thick fibrous layer without cortical- spicules. Apart from the spicules it 
somewhat resembles the cortex of Craniella cranium, as represented in Bowerbank’s 
figures. In one of the specimens, however, it assumes over a small area the usual 
structure, though still remaining without cortical spicules. In the other no trace of the 
Craniella structure exists ; it is, however, in such an unusual state, being crowded with large 
embryos, that I hesitate to give their true taxonomical value to the differences it presents. 
The embryos are in different stages of development, and many of them so large, that 
escape, unless by perforation of the cortex, seems impossible ; one embryo indeed 
occupies a cavity which extends into the cortex, and is only separated from the exterior 
by a thin membrane. Many of the embryos are also crowded with spicules, and thus it 
may be possible that the supply of silica obtained by the mother-sponge has been 
exhausted by the embryos in forming their skeleton, and thus fresh spicules to replace those 
^ Ann. and Mag. Nat. Hist., ser. 5, vol. ix. p. 149, 1882. 
