140 On Fossil Sponge-spicules of the Greensand. 



Plate VIII. 



Fifjs. 19-29. Fragments of silicified fibre. Figs. 19 & 24 show how small 

 spicules are often adherent to them. Figs. 20 & 24 show how 

 the little siliceous halls of Geodidte are often adherent to them. 

 Fig. 20 is an exti-emely common fonn, varjing slightly in its 

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

 part of the siliciiied fibre of a DadylocaJi/cites ; but whether to a 

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

 Ignorant. Figs. 2.5 & 26 show how small spicules are sometimes 

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

 ' a foramen (a) in the fibre, a ver\' common occurrence, as may be 

 inferred, in the silicified fibre of the Coralliospongite. 



Plate IX. 



Fig. 30. Hextemate head expanded regularly and horizontally. 



Fif/. 31. Hextemate head, of smaller dimensions. 



Fig. 32. Hextemate head of long shaft (fig. 66), iiTCgidar. 



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



tylocalyx Boicerhaiihii. 

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



lines b ab, b a b, and ba b showing that the branching of the 



axial canal, if thus earned on, would give the minute " biter- 



nate " fonn in Aphrocallistes Beatrix, Gray (Bowerbank, /. c). 

 Fig. 35. Hextemate head of long shaft, in-egular. 

 Fig. 36. Temate 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 Parfittii. 

 Fig. 39. The same, with fi-agment of shaft, lateral view. 

 Fig. 40, Disk of Dnctylocalycites callodiscns. 



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

 Fig. 43. Bihamate spicule, Fsperites hahlonensis. 

 Figs. 44 & 45. Four-rayed monUiform spicule, Mo7iilites quadriradicttus ; 



two views. 

 Figs. 46 & 47. Curved moniHform spicule, Monilites hciklanemis ; two 



forms. 

 Fig. 48. Small acerate spicide. 

 Fig. 49. Small curved acuate spicule. 



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

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



of many sizes. 

 Fig. 54. Eroded form, apparently, of fig. 40. 

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



views respectively. Geodites haldonensis. 

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



sizes. 



Plate X. 



Figs. 58-68. Shafted spicules, Geodites haldmetm's. Fig. 58. Tj-pical 

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

 fomi. Fig. 60. Piegular fomi, smaller. Fig. 61. Trifid, extended 

 cup-shaped. Fig. 62. Tiifid, recurved, anchor-shaped. Fig. 63 

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

 (varieties 'f). Fig. 66. Hextemate, vase-shaped, closely allied 

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



