140 On Fossil Sponge-spicules of the Greensand. 



Plate VIII. 



Figs. 19-29. Fragments of silicified fibre. Figs. 19 & 24 sliow liow small 

 spicules are often adherent to tliem. Figs. 20 & 24 sbow how 

 the little siliceous balls of Geodidse are often adherent to them. 

 Fig. 20 is an extremely common fonu, varying slightly in ita 

 detail, but so numerous as to be quite characteristic of some 

 part of the silicified fibre of a Dactijlocalycites ; but whether to a 

 particulai' species, or to what part of the fibre, I am equally 

 Ignorant. Figs. 25 & 26 show how small spicules are sometimes 

 incorporated with them, as in AphrocaUistes &c. Fig. 20 shows 

 a foramen {a) in the fibre, a very common occurrence, as may be 

 inferred, in the silicified fibre of the Coralliospongia). 



Plate IX. 



Fig. 30. Ilexternate head expanded regularly and horizontally. 



Fig. 31. Ilexternate head, of smaller dimensions. 



Fig. 32. Hexternate head of long shaft (fig. 06), irregular. 



Fig. 33. Hexternate head, stout, like the circumference-spicule of Dac~ 



tylocolyx Bowerbatikii, 

 Fig. 34. Hexternate head of long shaft, with blunt points, the straight 



lines b ab, b ab, and bub showing that the branching of the 



axial canal, if thus carried on, woidd give the minute " biter- 



nate " form in AphrocaUistes Beatrix, Gray (Bowerbank, I. c). 

 Fig. 35. Hexternate head of long shaft, irregular. 

 Fig. 36. Ternate head, with expanded, long, straight, attenuated arms, 



somewhat inclined forwards, and long shaft. 

 Fig. 37. Quatemate head, with fragment of shaft. 

 Fig. 38. Quaternate head of fig. 39, end view. Gomphites Parjittii. 

 Fig. 39. The same, with fragment of shaft, lateral view. 

 Fig. 40. Disk of Dactylocahjcites callodiscus. 

 Figs. 41 & 42. Lateral and end views respectively of D. elhpticus. 

 Fig. 43. Bihamate spicule, Esperites haldonensis. 

 Figs. 44 & 45. Four-rayed moniliform spicule, Monilites qtiadriradiattts ; 



two views. 

 Figs. 40 & 47. Curved moniliform spicule, Monilites haldonensis ; two 



forms. 

 Fig. 48. Small acerate spicule. 

 Fig. 49. Small curved acuate spicule. 



Figs. 50-52. Small spicules, more or less fragmentary or worn. 

 Fig. 53. Curved cylindrical smooth spicule, with obtuse ends ; numerous, 



of many sizes. 

 Fig. 54. Eroded form, apparently, of fig. 46. 

 Figs. 55 & 56. Largest form of siliceous ball of Geodia ; lateral and upper 



views respecti^el}'. Geoditcs hiddonensis. 

 Fig. 57. Smallest form of curved acerate spicule ; numerous, and of many 



sizes. 



Plate X. 



Figs, 68-68. Shafted apicides, Geodites haldonensis. Fig. 58. Typical 

 form, hexternate head extended, vase-shaped. Fig. 59. Irregular 

 form. Fig. GO. Regular form, smaller. Fig. 61. Trifid, extended 

 Clip-shaped. Fig. 62. Trifid, recurved, anchor-shaped. Fig. 63 

 The sanie, a little varied in form. Figs. 64 & 65. Bifid spicules 

 (varieties ?). Fig. 66. Hexternate, vase-shaped, closely allied 

 to the type form, fig. 58 (for end view see fig. 32). Fig. 67. Trifid 



