324 



A. W. WATEKS ON FOSSIL CHILOSTOMATOTJS 



Aperture 0*46 millim. long. 



Loc. Oligocene (Bartonian), Val di Lonte (Rss.), Brendola, Colle 

 Berici, Ferrara di Monte Baldo (A.-W.-\V. coll.) ; Miocene, Nussdorf 

 (Manzoni), Orakei Bay (JStol.), Mount Gambier (Lond. Geol.Soc. coll.). 



19. Membkanipoea arotts, d'Orb. (in Vincularice forma). Plate XIV. 

 figs. 20, 21. - 



Vincularia argus, d'Orb. Pal. Franc, p. 253, pi. dclxxxix. 

 figs. 1-4. 



Zoarium erect, slightly compressed. Zocecia quincuncially ar- 

 ranged in longitudinal lines, distinct, irregularly hexagonal, con- 

 tracted below, not raised above the general surface. Aperture oval, 

 occupying about one third of the zocecium. Two distal rosette 

 plates near the centre of the distal wall ; lateral rosette plates 

 several close together (fig. 20, a). 



This differs from M. macrostoma in having a very much smaller 

 aperture, which is not in so deep a depression. The aperture is 

 0-31 millim. long. 



Loc. Cretaceous, Meudon (cVOrb.). 



20. Membranipora concameeata, sp. nov. (in Vincularice forma). 

 Plate XIV. figs. 22, 23. 



Zoarium slender, erect, hexagonal in section, dividing dichoto- 

 mously, about 0*5 millim. in diameter. Zocecia in longitudinal 

 lines quincuncially arranged, distinct, with raised border, concave, 

 elongate, contracted slightly below ; border much raised above the 

 aperture, forming a raised arch. Aperture oval, occupying from one 

 third to one quarter of the length of the zocecium. Zocecial avicu- 

 larium at the junction of each branch. One distal rosette plate 

 near the centre of the zoarium (fig. 23) ; two lateral rosette plates 

 (fig. 22, a). 



This is the most common fossil in the material, and much resem- 

 bles Vincularia gracilis, d'Orb., from the White Chalk of France, 

 but differs in being smaller and having a smaller aperture, and 

 having six cells in a series instead of eight ; but we now know that 

 this last is not an important difference ; perhaps the two should be 

 considered varieties of one species. 



Aperture 0*14 millim. long. 



21. Membranipora ltjsoeta, sp. nov. (in Vincularice forma). Plate 

 XIV. fig. 14 ; Plate XVIII. fig. 82. 



Zoarium cylindrical, jointed, dichotomously dividing. Zocecia 

 suboval, rounded above, contracted below, distinct, surrounded with 

 an elevated margin raised above the aperture. Aperture large, about 

 one third the length of the zocecium, oblong, rounded at the corners, 

 contracted towards the middle. Very large elevated zocecial avicu- 

 laria directed downwards, with acute mandible. 



Aperture 0*2 millim. long, 0-11 wide. 



The form of the cell suggests a battledore, or, better, snow-shoes ; 

 and therefore, finding some difficulty in giving a distinctive name not 



