MARINE POLYZOA. 23 



PL XXIII. fig. 1, is shown the mode in which the polyzoary seems 

 to originate in a single cell, which is attached by a corneous tube 

 to some foreign base. And in PI. XXVI. fig. 2, is shown a cu- 

 rious cup-shaped appendage attached by means of a similar tube 

 to the bottom of a cell. 



3. SCRUPOCELLARIA. 



Cells rhomboidal, with a sinus on the outer and hinder 

 aspect ; each furnished with a sessile avicularium at the upper 

 and outer angle, and with a vibraculum placed in the sinus on 

 the outer and lower part behind. Aperture oval or subrotund, 

 spinous above, with or without a pedunculate operculum. Cells 

 biserial and numerous in each intemode. 



Scrupocellaria, Van Beneden, Recherch. 43; Gray, List of Brit. 



Rad.B.M. 111. 

 Bicellaria, sp. Blainv. 1830. 

 Cellularia, sp. Pallas ; Flem. 

 Cellaria, sp. Soland.; Lamk. 1816. 

 Scruparia, sp. Oken, Lehrb. Nat. 90, 1816. 



This natural genus is characterized more particularly by the 

 presence upon each cell of a sessile avicularium, seated, or in fact 

 forming the upper and outer angle, and of a vibraculum placed 

 on the back of the cell. The cells in some species are provided 

 with a pedunculate operculum, by which it is intended to desig- 

 nate a process, which arising by a short tube from the anterior 

 wall of the cell, immediately beyond the inner margin of the 

 opening, projects forwards and bends over the front of the cell, 

 expanding into a variously-formed limb, and serving as pro- 

 tection to the mouth of the cell in front. The cavity of the tube 

 by which the process arises, becomes, in the expanded portion, 

 continuous with variously disposed grooves or channels which 

 terminate at the edges of the operculum. This organ affords 

 excellent specific characters (not in this genus alone). Besides the 

 sessile avicularia above noticed, many species of this genus also 

 possess avicularia of another kind, and which are placed on the 

 front of the cell below r the opening and towards the inner side, or 

 in other words, towards the middle line of the branch. In this 

 genus, in all those species in which the second avicularium occurs, 

 ' each individual cell is provided with one. This additional avi- 

 cularium appears to be composed of a flexible material, and it is 

 very easily broken off, so that in many instances, perhaps 

 throughout an entire specimen, the organ itself may be wanting, 

 although its position is clearly evidenced by the existence of a 

 rounded opening in the usual situation of the organ. It is ne- 

 cessary to distinguish this form of flexible (if such it be) avicu- 



