Natural History of East Finmarh. 97 



base of each papilla is a pore in the calcareous front wall " ; 

 but he adds : " It has usually been assumed that the radiating 

 series of pores correspond with slits between the bars ; but 

 in C radiata there can be no doubt that the pores are in the 

 same radii as the membranous marginal spines." "The 

 lateral junctions of the frontal bars are indicated by prominent 

 radial ridges, each of which rises to a small tubercle just 

 inside the line of the membranous papillae above described. 

 The pores consequently lie, as described by other observers, 

 in radiating furrows. That the union between the bars has 

 not been complete is indicated by the fact that a thin line of 

 air in some cases underlies the ridge." Thus Dr. Harmer 

 considers that this particular form totally differs from ordinary 

 Cribrilinidae in that the line of lacunes is here the centre of 

 the bar, and that the ribs are its sides. My own conclusion is 

 different. I regard these papillae as really in the line of junc- 

 tion of the bars. It is my endeavour to show in these notes that 

 all the different Cribrilinidan forms depend upon the different 

 structural building up of the bars which we first meet with 

 in their simplest form in Leprulia n'ltida, and that the bars 

 may be invariably recognized by their basal loop, which usk ally 

 has its origin in the side wall ; but in cases ivhere the Cribrili- 

 nidan structure occupies only the central part of the front wall 

 the loop of the bar will be found buried in that front wall. If 

 the illustration (PI. IX. fig. 3) which I have given of a portion 

 of the front wall of innominata be now referred to, it will be 

 seen that three bars are represented with their basal loops 

 situated in the side wall, that at the inner end of the loop 

 there is a minute pore, and a line passes down the centre of the 

 bar indicating the lumen beneath"^. Between the bars (that 

 is, at their junction) is the usual line of lacunes ; between the 

 loops of the bars, and excluded from the normal Cribrilinidan 

 structure by the fact that the arch which connects the bars 

 passes inside them, are the papillee {a, b, &c.), which are thus 

 in the line of, but really outside of the junction of the bars 

 which form, the lacunes. If an opening (c), from which 

 the papilla has been removed, be examined it will be found 

 to be inside of the side wall, and that it is directed inwards 

 and downwards so as to pass into the body-cavity. Now if 

 the bars and their lumen represent the spines of what have 

 been called Membraniporidie, and if the lacunes with the line 

 which passes through them be the junction- line of two adjacent 

 bars, then these papillae cannot represent the spines. What 

 are they then ? Their resistance in boiling liquor potassoe 



* The " thin liue of air " which Dr. Harmer observed was, in my 

 opinion, in this lumen. 



Ann. (jt j\[ag. N. Ilist. Ser. 7. Vol. xii. 7 



