AND PHYSIOLOGY OF THE SPONGIADtE. 
833 
Bicalcaeate bihamate (Plate XXXVI. fig. 27). — This singular and minute form of 
spiculum has hitherto been found only in Isodictya Normam, Boweebank, MS. A new 
British species. 
Expando-teidentate equi-anchoeate (Plate XXXVI. fig. 28). — From an undescribed 
sponge in the British Museum. The shaft of this minute spiculum is frequently curved 
to the extent of nearly a semicircle. Expando-bidentate forms are also mingled with 
the tridentate ones. 
Teidentate fimbeiated EQUi-AJsrcHOEATE (Plate XXXVI. fig. 29).— From Isodictya 
jimbriata^ Boweebank, MS. Shetland. The singular fimbriation of the shaft of the 
spiculum has never been observed in any other anchorate spiculum. In this sponge 
the spicula of this form may be traced from the earliest stage of development to the 
fuUy fimbriated form exhibited by the one represented by fig. 28. They are very 
abundant on the interstitial and dermal membranes, and mixed with them ; there are 
many that are only bidentate, but are as completely fimbriated as the tridentate ones. 
The fimbriae are very delicate and translucent, and require a careful management of the 
light to render them apparent. 
Quadeihamate (Plate XXXVI. fig. 30). — From Hyalonema mirabilis, Geay. These 
very minute spicula are dispersed in considerable numbers on the interstitial membranes 
of the sponge. 
iNEQTJi-TEiEOTUiiATE (Plate XXXVI. fig. 31). — From an undescribed sponge in the 
cabinet of my friend Mr. Geoege Clifton, of Freemantle, Western Australia. In 
Plate XXVI. fig. 38 I have figured a more fully developed specimen of this form, and 
described it in the ‘ Philosophical Transactions ’ for 1858, page 319, believing at that 
time that it was probably derived from the ovarium of a Spongilla. From the struc- 
tural differences of the two specimens, it is probable that the former one is not from the 
same species of sponge as the latter. 
Eccenteic teieotulate (Plate XfXXVI. figs. 32 & 33). — From the same sponge as 
fig. 31. Fig. 33 presents the fully-developed axial eccentricity, while the axis in the 
spiculum represented by fig 32 is both centrical and eccentrical, and these variations in 
the mode of the development of the rotulse are exceedingly common. 
Cylindeo-ceucifoem (Plate XXXVI. figs. 34, 35, 36, 37). — From Hyalonema mira- 
bills, Geay. British Museum. These four forms occur in considerable numbers, either 
imbedded in, or immediately surrounding the thick coriaceous sheath which envelopes 
the spiral column that is projected from the base of the sponge through its centre. 
All the imaginable varieties of form between figs. 34 and 37 are found mixed together ; 
and they appear to be especially abundant around that part of the column which is 
imbedded in the midst of the sponge. The cylindrical form represented by fig. 34 is of 
rare occurrence without a slight indication near the middle of the absent third and 
fourth rays of the perfect cruciform spiculum. 
Spiculated cylindeo-ceucifoem (Plate XXXVI. fig. 38). — From Hyalonema mirabilis^ 
Geay. British Museum. This spiculum is from the sheath of the same sponge as 
