SEA-URCHINS AND SEA-CUCUMBERS. 299 



specimen of which is in my possession, but I have vainly- 

 examined the skin for any structure analogous to this.* 

 In the Mediterranean species the skin, especially of the 

 belly-side, is described as filled with plates exactly re- 

 sembling broad and thin wheels of glass, supported by 

 four, five, or six radiating spokes, and having the inner 

 edge of the hoop cut into teeth of exceeding delicacy. 



Another animal remarkable for the furniture of its skin 

 is the genus Synapta, which is very similar in form, and 

 closely allied to the Chirodota. It is very common in the 

 Adriatic and Mediterranean seas, but has not yet been 

 taken on the British coasts. I would counsel you, how- 

 ever, to have your eyes open if you have the opportunity 

 of searching our coasts ; for, as Muller found one species, 

 the Synapta iriharens, on the shores of Denmark, it is not 

 at all unlikely that we may possess either it or some other. 

 Should it ever come into your hands, slit open the skin of 

 the belly, where you will find, imbedded in little papillae 

 or warts, some highly curious spicula 

 or calcareous forms. Each consists /5 s !) 



of an oblong plate, perforated with /jr JJ 



large holes in a regular manner, and 

 having a projection on its surface near 

 one extremity, to which is jointed a 

 second piece, having the most singu- anchoe-plate in synapta. 

 larly true resemblance to an anchor. The flukes of this 

 anchor project from the skin, the shank standing obliquely 

 upward from the plate, to which it- is articulated by a 

 dilatation, where the ring would be, which is cut into 

 teeth. \ 



* The most carefnl and repeated search has not availed me to 

 find in the skin the least trace of calcareous atoms ; but this may pos- 

 sibly be because I had unfortunately preserved my specimen in acetate 

 of alumina, and the acetic acid has perhaps dissolved the lime. 



t Since tie printing of the above, an admirable paper has appeared 

 in the proceedings of the Zoological Society of London, by Messrs. 

 Woodward and Barrett, " On the Genus Synapta," These authors in- 



