136 MEMBRANIPORID^. 



members of that genus and allies it to the present. 

 There is no essential distinction between M. catenularia 

 and such a form as M. mono st achy s, 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 figrnxd by Smitt *, branches 

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

 to tliem, 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 liippothocs. I have no 

 doubt that its proper place is amongst the Metnbrani- 

 p)or(E. 



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 zooecia 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. 



