Verrill, Azotes on Radiata. 379 



Dr. Albert Kolliker has recently investigated this interesting sub- 

 ject much more completely, both among Peiinatalacea and Al- 

 cyonacea, and has already published a short notice,* preliminary to a 

 more extended memoir upon it. For these reasons it will be passed 

 over in the following pages with only such descriptions of the exter- 

 nal appearance of the two forms of polyps as may be useful for the 

 dotermhiation of the genera and species. 



Renilla amethystina Vcniii. 



Bulletin of the Museum of Comp. Zool, p. 29, Jan. 1864; Proceedings Boston Soc 

 Nat. History, 1866, p. 326. 



Plate V, figure 1. 



Frond large, rather thin, broad reniform, broader than long, proper, 

 tion of breadth to length about as 1 -3 : 1 ; sinus extending more than 

 one third across the length of the frond, about equal to one third of 

 its breadth ; the posterior lobes broad and rounded, meeting behind _ 

 Peduncle placed at about its own diameter from the end of the sinus ; 

 length, in contraction, equal to about a third of the breadth of the 

 frond. Lower surface and peduncle rough with spicula, which are 

 arranged somewhat in radiating lines, upper surface slightly convex, 

 covered with very numerous, rather closely set, small polyps, which 

 are surrounded at base by slightly projecting, rigid calicles, strength- 

 ened by numerous spicula, which rise up in angular clusters. Thickly 

 scattered between the ordinary polyps are those of the second or rudi- 

 mentary kind, which form, in the contracted state, much smaller ver- 

 rucae, surrounded by a lower border of s^^icula, and consisting of clus- 

 ters of from eight to thirty, small, round paiiillse, each with a dark 

 point in the centre. 



According to Mr. Bradley's observations upon the living polyps, 

 these are mostly '25 of an inch long, and about '12 across the expand- 

 ed tentacles, the bodies of the polyps being about '06. " They are 

 transparent, with an opaque stomach, the eight radiating lamellse 

 showing through the walls ; around the small mouth, which is edged 

 vnXh white, are eight radiating white points, corresponding to the 

 intervals between the tentacles ; around the base of the tentacles is a 

 brown ring, which runs down in points opposite the spaces between 

 them. Opposite the base of each polyp are two (rarely four or five) 

 bunches of little white rays. The frond is nearly transparent, but highly 

 colored by very numerous purple spicula, evenly distributed on the 



* Verhandlungen der physik-medicin G-esellschaft in Wiirzburg, Dec, 1867. Also, 



Annals and Mag. Nat. Hist., March, 1868. 



