192 DR. HINDE A^D MR. HOLMES OK SPOKGE-EEMAINS 



PL YIII. fig. 21. Short, strongly curved acuate, upper half 

 evenly cylindrical, then gradually tapering, abruptly pointed. 

 Spines small, conical, numerous. Length "12 mm., thickness 

 •01 mm. 



PI. VIII. fig. 34j. Slightly curved acuate, gradually tapering 

 from the rounded summit ; surface evenly covered with minute 

 spines. Length -185 mm., thickness -015 mm. 



PI. YIII. figs. 35, 36. Elongate acuate, upper portion curved 

 with slightly inflated summit, lower two thirds nearly straight, 

 gradually tapering to an acute point. In the upper portion 

 short slightly hooked sp)ines ; in the lower the spines are smaller 

 and sparsely distributed. Length -51 mm., thickness '015 ram. 

 Fig. 36 is straight, spined like fig. 35. 



PI, VIII. fig. 30 a. Stout acuate, the upper portion bent 

 nearly at right angles, thickest at the head; from thence gra- 

 dually tapering to the apex, which is abruptly pointed. The bent 

 portion of the shaft is smooth, the rest with minute conical 

 spines ; near the apex there are small, thickly set, recurved spines. 

 Length -235 mm., thickness "02 mm. Mr. Carter figures spined 

 acuates of similar form, but larger, in Microciona intexta (Ann. 

 & Mag. Nat. Hist. s. 4, vol. xviii. 1876, p. 239, pi. xv. fig. 43 a). 



PI. VIII. fig. 31. Acuate spicule with the upper portion 

 strongly curved like a walking-stick, and furnished with minute 

 spines; in the straight lower portion of the shaft the spines are 

 fewer and smaller. Length -115 mm., thickness "014 mm. 



As shown in the figures on PI. VIII., acuate spicules, whether 

 smooth or spined, are very abundant in the Oamaru deposit ; and 

 they exbibit considerable variations in size, ranging in length 

 from '095 to 1'5 mm., and in thickness from -006 to "04 mm. 

 The greater number, however, range in length between "2 and 

 •5 mm., and they correspond very closely in this respect with the 

 acuate spicules of existing sponges. Acuate spicules are present 

 in numerous genera of recent sponges ; the most important of 

 these are Esperella, lophon, Usperiopsis, AmphiJectus, llyxilla, 

 Axinella, and Latrunculia ; also in some species placed by 

 Bowerbank and Carter under Salidiondria, Dicfyocylindrus, 

 Mymeniacidou, &c. Several of the above-named genera can be 

 recognized in the Oam.aru material by their distinctive flesh- 

 spicules, to be described later. 



Possil acuate spicules are known from the Carboniferous lime- 

 stone ; they are also present in Jurassic and Cretaceous strata ; 



