176 



HABDWICKE'S SCIENCE-GOSSIP. 



[Aug. 1, 1868. 



and in the mesentery of a species of Cidaris. "Dumb- 

 bell spicules" have been found in the ambulacral 

 tube of a species of Echinus from the New Hebrides, 



Fig. 181. Spicules from ambulacral 

 tube of Echinus from New Hebrides. 



Fig. 182. Spicule of 

 Diadema sp. 



and T-shaped spicules in the intestines of Gonio- 

 eidaris geranoides. Other forms, approximating 



Fig. 183. Spicules of Cidaris Fig. 184. Spicules from 

 grandis. intestine of Echinometra. 



more to perforated plates, occur in the intestines of 

 a species of Echinometra and of Cidaris grandis. 



Fig. 186. Spicules of 

 Synapta bidentata. 



Fig. 185. Spicules of 

 Goniocidaris geranoides. 



Fig. 187. Plates of Thyone 

 in course of formation. 



These figures are evidence, therefore, that spicules 

 of a very singular aud interesting form are to be 

 found in the interior of sea-urchins, or those 

 Echinoderms which belong to the order Echinoidea. 



Fig. 188. Body Plates 

 of Thyone flexus. 



Fig. 1S9. Plate of Foot 

 from Thyone flexus. 



More attractive are many of the calcareous forms 

 which occur in the sea-slug order — the Holothur- 



oidea aud " spicules of a Holothuria " are quite 

 stock objects with tbe opticians, to say nothing of 

 the anchors and plates of Synapta and the wheels 

 of Chirodota. We have, as indigenous British 

 species, about a dozen kinds of sea-cucumbers 

 (Peutacta), and half a dozen Holothurias and 

 Thyones, yet, singularly enough, we know nothing 

 of their spicules, excepting only Thyone flexus. 

 Here, therefore, is a fair held for work. 



Fig. 190. Anchor and Plate 

 of Synupta inharens. 



Fig. 191. Anchor and Plate 

 of Synapta digitata. 



But what of Synapta? Dr. M'Intosh fonnd in 

 the Outer Hebrides not only Synapta Galliennii, 

 which occurs also at Guernsey, but another species 

 which he calls Synapta Buskii, the plates of which 



Fig. 192. Plate of Synapta Buskii. 



have a long handle, and are accompauied by very 

 characteristic anchors. Synapta digitata is also 

 British, aud many of the slides which are sold are 

 referred to it. As an example' of another form of 



Fig. 193. Wheels of Myriotrochus 

 Rinkii. 



Fig. 194. Wheel 

 of Chirodota violacea. 



plate which accompany similar anchors, we give 

 a figure of the anchor and plate of Synapta inJuerens, 



