MARINE POLYZOA. 



s. Vert. t. ii. p. 180) is equally an indisputable member of the 

 same genus, its identification, from the description there given, 

 with any of the species here enumerated, does not appear to be 

 possible. There seems little reason for referring his Cell, vesicu- 

 losa to the genus at all, as in that species, it is said, the articula- 

 tions appear to be formed of two cells united. The Menipea hya- 

 l&a of Lamouroux (Polyp. Flex. p. 146. pi. 3. fig. 1), though in the 

 figure exhibiting some faint traces of the aspect of a Caienicella, 

 cannot safely be referred to that genus ; neither, most probably, 

 can Eucratea cordierii, Audouin (Savigny, Egypt, p, 13. fig. 3), 

 which latter would seem to form the type of an as yet unde- 

 scribed genus. In Catenicella each cell arises from the upper and 

 back part of another by a short corneous, tube, which is prolonged 

 from the interior of one cell to that of the one above. The cell 

 is furnished on each side at the top with a usually well-developed 

 avicularium, in some species of huge size, and in some very mi- 

 nute or entirely aborted. This avicularian process, which is 

 sometimes closed above and more or less elongated upwards, con- 

 stituting a conical or acerose spine, is sometimes open above, 

 assuming the form of a shallow cup or receptacle. In some spe- 

 cies both modifications of this portion of the lateral process are 

 met with in the same specimen. This form of spine or cup, as 

 the case may be, is always distinctly separated from the cavity of 

 the avicularium itself by a calcareous septum. Below the avicu- 

 larium there is also in many cases a third distinct cavity, usually 

 widely open, the opening being occasionally covered in by a con- 

 vex transparent membrane, and its bottom apparently perforated 

 by several minute foramina. It is thus correct to say, that each 

 cell is furnished with two lateral processes, each of which, in the 

 fully developed state, consists of three distinct compartments, 

 one superior, a cup or spine ; a middle one, which is the avicu- 

 larium ; and an inferior. And it would appear that one or more 

 of these elementary compartments of the lateral process may be 

 more developed than the next, or sometimes more or less com- 

 pletely aborted. The mouth of the cell is situated at the upper 

 part, and is of the same conformation as in the rest of the Chei- 

 lostomatous suborder. An important generic character consists 

 in the gemination of the cell at each bifurcation. 



These characters are common to all the species included in the 

 genus, which furthermore admits of being subdivided into three 

 extremely natural sections or subgenera. These subdivisions are 

 named respectively the " Fenestratae," the " Vittatse," and the 

 " Simplices." In the fenestrate division the cells are of larger 

 size and stronger than in the others, and the wall of the cell ap- 

 pears to be constituted of at least two distinct laminae. The ex- 

 ternal lamina on the front of the cell is perforated by a certain 



