IN THE LOWER TERTIARY STRATA OF NEW ZEALAND. 233 



Proc. Zool. Soc. 1869, p. 3il, pi. xxiv. fig. 6), from the Seyc-helle 

 Islands. It is evident, however, that these spicules belong to 

 Tetractinellid sponges, and in the position and character of the 

 trifid rays they bear a certain resemblance to the spicules of 

 Triptolemus, Sollas, with the difference, however, that there are 

 two whorls of trifid rays instead of one. This difference seems 

 to be of generic value, and we therefore j)ropose to consider these 

 double-trifid spicules as belonging to a new genus and species 

 under tlie name of Ditricenella Oamaruensis. 



Ditricenella (a). — PI. XII. fig. 36. Spicules of the same 

 character as the preceding, but very much smaller ; the shaft 

 and rays are armed throughout with conical spines ; the rays of 

 the whorls are simple, and not furcate. Length of spicule '059 

 mm., thickness of shaft '007 mm. Length of rays "023 mm. 



Aceraie and Trifid Spicules q/'Greodites, Carter, Stelletta, 

 Osc. Sell., and allied Genera. 



PL XIII. figs. 1, 2. Pusiforra acerate spicules, smooth, slightly 

 curved, tapering to acute points. Length from 1"55 mm. to 3*25 

 mm., thickness about '1 mm. The larger size of the spicules as 

 compared with the corresponding forms figured on PI. VII., indi- 

 cate that they belong to Tetractinellid sponges. These spicules are 

 common to several genera of this division. There are in the 

 deposit numerous forms intermediate in size between those 

 figured. 



Geodites (a). — PL XIII. figs. 3, 4, 5. Trifid spicules with 

 slightly curved tapering shafts and short head-rays projecting 

 obliquely forwards. The rays are either simple (fig. 5) or furcate 

 (fig^. 3, 4). Length of spicules 2*7 mm. to 3"95 mm., thickness 

 of shaft 1 mm. ; length of head-rays "25 to '32 mm. These 

 three forms probably belong to the same species. 



PL XIII. fig. 19. Anchor trifid spicule ; shaft straight, slender, 

 very gradually tapering, head rounded, the three simple rays 

 evenly recurved. Total length uncertain, thickness of shaft 'OS 

 mm., length of head-rays '24 mm. This form probably belongs 

 to the same species as the trifid spicules referred to above. 



Similar detached trifid spicules have been described by Mr. 

 Carter from the Lower Grreensand of Haldon, Devonshire, under 

 the name of Geodites Saldonensis (Ann. & Mag. Wat. Hist. s. 4, 

 vol. viL 1871, p. 129, pi. x. figs. 58-67) ; they also occur in the 



