305 



Genera. 



A more or less prominent tube-sha])ed peristome, proximally to 

 which is found an ascopore: 



A simple separable operculum, no vestibular arch, no avicularia 



TubiicelUtria d'Orbigny. 



A membranous opercular valve (?), a vestibular arch, each zoa-cium 

 with one or two avicularia at the height of the ascopore Tubipordlu n. g. 



Tubucellaria opuntioides Pallas. 



Busk, Challenger, Zoology, Vol. X, part 1, 1884, p. 100, 



PI. XXIV, fig. 7, PI. XXXVI, fig. 19, pars. 



(PI. XVI, figs. 4 a— 4 d). 



The zooecia elongated rhombic, arched, surrounded by weakly projecting 

 edges. The pore-pits, which have a very small pore, are round or oval, and their 

 network of separating ridges is beset with fairly large, scattered tubercles, of 

 which 3—6 may surround each single pit. The obliquely ascending, tube-shaped 

 peristome, which as a rule has a circular aperture and the distal wall of which 

 is only to a small extent freely projecting, is contained 5 — 6 times in the length 

 of the actual zoavial tube. It shows a number of more or less sharp longitudinal 

 ribs, the furrows separating which contain 2 — 4 larger or smaller pits. Proximally 

 to the peristomial tube there is a more or less distinct, narrow, curved ridge 

 (fig. 4(1), which connects the two marginal ridges. A little proximally to this lies 

 the ascopore, which is surrounded by a more or less prominent, wall-like margin, 

 often beset with tubercles. Its opening on the inner surface of the zooecium is 

 provided with a distal, arched, half-roof. The somewhat ascending distal wall is 

 provided with a large, triangular, oval or trapeziform, multiporous rosette-plate, 

 which is divided by a network^ of ridges into a number of larger and smaller 

 areas. The distal half of each lateral wall bolh on its abaxial and on its adaxial 

 part is provided with 2 — 4 scattered rosette-plates with 2 (1)— 6 pores, so that 

 not only two neighbouring zocccia, but also two zooccia placed at the same level 

 and separated by a neighbouring zocrcium are thus connected with one another 

 by means of rosette-plates. The operculum which is not strongly chitinized 

 makes a segment a Utile larger than a semicircle and the two lateral margins 

 are feebly convergent towards the proximal margin. A very low, almost rudiment- 

 ary opercular arch is placed a little distally to the median part of the operculum 

 and a muscular process is found on each side within the lateral margin. 



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