136 MEMBRANIPORID.E. 



members of that genus and allies it to the present. 

 There is no essential distinction between M. catenulttria 

 and such a form as M. monostachrjs, which also takes on 

 not unfrequently the characteristic habit of Hippothoa. 

 There is, indeed, a difference in the mode of branching ; 

 but in a variety of M . pilosa figured by Smitt *, branches 

 are given off from the sides of the cells and at right angles 

 to them, in the most typical Hippothoan fashion; and 

 therefore we cannot use this character as a diagnostic. In 

 the present form the cell is more or less produced below, 

 but there is no approach to the thread-like prolongation 

 which distinguishes the true Hippothoa. I have no 

 doubt that its proper place is amongst the Membrani- 

 por<B. 



There is a great tendency in this species to the massing 

 together of the cells, which often form a continuous 

 expansion of considerable extent. In such cases the 

 branch lines of cells, which are very numerous, take an 

 upward direction, and are brought into close union, so as 

 to constitute what seems to be a solid crust of somewhat 

 fan- shaped figure. In other cases a different habit prevails, 

 and the zoarium covers the shell, which it incrusts, with 

 a very pretty dendritic pattern. 



In many of the zoo3cia the area is completely closed in 

 by a solid calcareous covering. I have never met with 

 the spine below the aperture, as figured by Smitt f, on 

 any specimen which I could refer to this species. 



* Krit. Forteckn. iii. pi. xx. fig. 49. 

 t Loc. cit. pi. xx. fig. 46. 



