IN THE LOWER TERTIARY STRATA OP NEW ZEALAND. 249 



this spicule when complete, the greater number have been broken 

 off. Leugth of spicule "1 mm., width across rays '05 mm., length 

 of rays •045 mm., thickness of shaft '005 mm. 



Syalonema (h). — PI. XV. fig. 26. Small amphidisc, shaft 

 smooth, with slightly convex discs at either end, and 8 or 10 

 slightly projecting curved rays. Somewhat similar amphidiscs 

 are present in Hyalonema Thomsoni, Marshall (see Chall. Eep. 

 vol. xxi. pi. xxxiv. fig. 7). Length of spicule *056 mm., width 

 across summit "023 mm., thickness of shaft "003 mm. 



The number and variety of form of the amphidisc spicules 

 referred to above indicate that the hexactinellid sponges to which 

 these flesh-spicules belong were numerously represented in the 

 Oamaru strata. lu all, 9 examples are figured, indicating pro- 

 bably 5 or 6 species. The principal recent genera characterized 

 by ainphidiscs are Syalonema, Gray, Pheronevia, Leidy, and 

 &emperella. Gray ; and it is probable th.at most of our fossils 

 belong to the first named, though it is certain that one species of 

 JPlieronema is present. None of the fossil amphidiscs is suffi- 

 ciently similar to any of the recent to be considered as belonging 

 to the same species. Fossil amphidisc spicules are extremely 

 rare, but an undoubted cast of one has already been described by 

 Wisniowski from Jurassic strata at Cracow (Jahrb. der k.-k. geol. 

 Eeiclisan. Wien, Band xxxviii. 4 Heft, p. 679, pi. xii. fig. 38). 



Scopule Flesh- Spicules of Hexactinellid Sponges. 



Aphrocallisfes (a). — PI. XV. fig. 24. Shaft incomplete; the 

 upper portion of the spicule consists of four simple rays, which 

 curve gracefully outwards ; they are thickest at their bases and 

 gradually taper upwards, terminating in a small bead-like infla- 

 tion. The surface of these rays is minutely tuberculate. Length 

 of rays "07 mm., thickness at base -01 mm., thickness of shaft 

 •0056 mm. The scopules in recent hexactinellids nearest to this 

 form occur in AphrocalUstes Bocagei, "Wright (see Chall. Eep. 

 vol. xxi. pi. Ixxxiv. fig. 3), from Japan, and in Chonelasma hamatum, 

 Schulze {I. c. p. 323, pi. xci. fig. 4), from the South Pacific, at a 

 depth of 630 fathoms. 



PI. XV. fig. 25. Scopule with cylindrical, slightly curved 

 shaft, the summit of which is inflated and supports four straight 

 simple cylindrical rays, which slightly diverge from one another 

 above. These rays are minutely tuberculate, their summits are 



