TN THE LOWER TERTIART STBAT.^ OE NEW ZEALAND. 251 



PL XV. fig. 32. Spicule probably six-rayed wben complete, 

 tlie rays slender with occasional large spines. Length of rays 

 •047 mm., thickcess -005 mm. Spicules similar in form but for 

 the most part larger are present in Semperella claviformis, G-ray 

 (Ann. Mag. Nat. Hist. s. 4, vol. x. 1872, p. 7G). 



PI. XV. fig. 33. Two slender five-rayed spicules, spined like 

 the preceding. The spicules are in their natural position with 

 respect to each other. 



Mesli-SpicuJe of Hexactinellid Sponge. 



PI. XV. fig. 34. A fragment of spicular mesh of a Dictyonine 

 hexactinellid in which the rays are minuttly spined or tubercu- 

 late. Thickness of rays "036 mm., distance from node to node 

 •22 mm. Sm.all pieces of spicular mesh are common enough in 

 the Oamaru material, but they are always mere fragments, hardly 

 a single square being preserved entire. There is no apparent 

 reason for this minute disintegration of the comparatively strong 

 portion of the sponge-skeleton when one considers the perfect 

 state of preservation of so many of the delicate flesh-spicules. 



Anchoring-Spicules of HexactinelUd Sponges. 



PI. XV. fig. 22. An imperfect anchoring-spicule showing the 

 distal end of the shaft with four openly cur^-ed, acutely pointed 

 rays extending, grapnel-like, from it. Both shaft andrays traversed. 

 by axial canals. "Width across rays 1 mm., length of rays '75 

 mm., thickness of shaft "1 mm. ^inchoring-spicules of this type, 

 but usually smaller than the form figured, are present in the 

 recent I^uplectella aspergillum, Owen (see Chall. Kept. vol. xxi. 

 pi. iii. figs. 22, 23). 



Pheroneona (a).— PI. XV. fig. 23. Spicule imperfect, consisting 

 of the distal portion of a barbed shaft, which becomes thicker 

 near the end and is harpoon-shaped with two prongs or rays, 

 one of which is partially broken. The rays are smooth and re- 

 curve at an acute angle. The shaft has a wide axial canal, which 

 at the end becomes bulbous, with a minute diverticulum at either 

 side and one above. Length of head-rays '078 mm., thickness of 

 shaft -017 mm. This sjjicule belongs either to the basal tuft or id 

 one of those which project laterally from tlie surface of the sponge. 

 Kecent spicules of this type are much larger than the form figured, 

 such as those of JPJieronema Anncs, Leidy (see Chall. Eep. pi. xii. 

 fig. 7), and of P. Gragi, Sav. Kent (Monthly Micros. Juurn. 1870, 

 p. 243, pi. 63. fig. 16), from the coast of Portugal. 



