320 



A. W. WATERS ON FOSSIL CHILOSTOMATOUS 



amined I have found one form constant : the fistulosa from the 

 Mediterranean has its rounded avicularium above the zooecium ; the 

 sinuosa has a diagonal avicularium pointed downwards, with the 

 lower part raised ; the Johnsoni, from Rapallo (Italy) and New 

 Guinea, has a zocecial avicularium with a projecting hood above, 

 as figured by Hincks. I find my observations on the recent species 

 entirely confirmed by the examination of a large number of fossil 

 forms. 



Some thick specimens, such as fig.l, have the characteristic avicu- 

 laria of the European fistulosa ; these are somewhat rare ; but slender 

 specimens, such as fig. 12, are common, and probably these are the 

 same species ; but as I have been unable to find any avicularia in 

 these, both from Yarra-Yarra and Mount Gambier, the point can- 

 not be decided with certainty. In the specimens figs. 10, 11, how- 

 ever, I find a small wide avicularium, as in larger fistulosa, with 

 which these must therefore be united. The shape of these last 

 resembles that of C. Johnsoni, which is the C. mavginata, Reuss 

 (Tert. Wien, p. 59, pi. vii. fig. 29, not 28) ; and I have slender 

 C. Johnsoni from off Raton (New Guinea) resembling figs. 10, 11 

 in all except the avicularium, which is the large rounded one with 

 which we are already acquainted in 0. Johnsoni. 



In fig. 11 we have an interesting specimen, as showing how very 

 slender they may sometimes be; this has only one longitudinal 

 row of cells on each of the four faces. In specimens from Mount 

 Gambier, like my fig. 12, I have occasionally found in the oral 

 aperture two teeth above and two teeth below, and in the ovarian 

 openings sometimes one set of teeth, sometimes two ; but these 

 cannot be looked upon as constant characters, and lead us to think 

 that C. crassa must be considered a doubtful species ; or perhaps 

 two species are represented, seeing that avicularia of two kinds 

 are figured. I also sometimes find in the recent G. Johnsoni, from 

 Rapallo, two such teeth in the upper part of the aperture, as well as 

 the two below. 



Pig. 1 shows that the joints of this specimen were attached by nu- 

 merous horny tubes. In recent C. tenuirostris and C. malvinensis the 

 joints are usually thus attached ; but this is not the case inC. fistulosa ; 

 but in specimens of C. Johnsoni, from Rapallo, there are sometimes, 

 though not usually, several such connecting tubes. This leads us 

 to the consideration of these joints ; for when a stem divides and 

 two new branches are formed, the calcareous wall is continuous, 

 and in some the branches are already large (perhaps throwing out 

 fresh branches) before this calcareous wall is broken through. Of 

 specimens I examined, I found this calcareous structure remained 

 continuous longest in C. Johnsoni, but scarcely at all in C. gracilis, 

 while C. fistulosa occupied a mean position ; but much might de- 

 pend upon the sea in which each specimen grew, as jointed structure 

 in this and other genera must be looked upon as an adaptation to 

 moving water. In fossil specimens from the Pliocene &c. perma- 

 nent ankylosis, as already pointed out by Busk and Hincks, is 

 frequent. I 'am not inclined to think that, as a rule, articulation 



