320 



Exochella Jullien\ char, emend. 



The primary aperture, which is provided with 2—5 jointed spines, is separ- 

 ated by a distinct boundary from the peristome and furnished with a distinct, 

 but not stronglj' developed vestibular arch. The operculum is slightly chitinized 

 and not distinctly marked off from the compensation-sac. The peristome has 

 three, sometimes coalesced teeth, a median and two lateral, which may appear 

 again with greater or less distinctness in a secondary peristome. Normally there 

 is an avicularium on each side, but in more or fewer zooecia the one or both 

 may be absent. There is' apparently a membranous ectoocecium and in the distal 

 half of the zooecium there are 3 large, multiporous pore-chambers. 



Exochella triccuspis Hincks. 

 Mucronella tricuspis Hincks, Annals Nat. Hist. ser. 5, Vol. VIII, 

 1881, p. 125, PI. Ill, fig. 1. 

 (PI. XVII, figs. 9 a— d). 



The zooecia, broadly rhombic, evenly arched, often with more or fewer, larger 

 or smaller tubercles of varying form. A raised marginal line is as a rule indis- 

 tinct and the marginal pores in part difficult to observe. The primary aperture, 

 whitfh has three spines, has a broad and low sinus (fig. 9 b) more or less sharply 

 marked off from the lateral margins ; in the full-grown zooecia it can be distinctly 

 seen through the frontal wall (fig. 9 a). The operculum (fig. 9 d) does not have 

 distinct muscular ridges. There is a well-developed, tube-shaped peristome, which 

 conceals the spines and the distal half springs from the fi-ontal wall of the dis- 

 tal zooecium or in the ooecium-bearing zooecia from the proximal part of the 

 ooecium. • 



The peristome is provided with three coalesced teeth, the central one widened 

 at the end, hammer-shaped, and connected at the widened end with the two short, 

 finger-shaped lateral teeth. Outside there is a new set of uncoalesced teeth, the 

 central one not widened whilst the two lateral are strongly truncate, rounded 

 projections. 



The ooecia are furnished with finely, radiating striae and enclose the spines. 



The avicularia, the narrow elongated mandible of which points outwards, 

 appear as a rule in pairs, sometimes almost at the same, sometimes at somewhat 

 different levels. 



Two small fragments from Victoria are to hand (Miss Jelly). 



» 45, p. 55. 



