320 



Exochella Jullicn', 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 strongly 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 (wiculariiim on each side, but in more or fewer zod'cia the one or both 

 may be absent. There is apparently a membranous ectooa?cium and in the distal 

 half of the zoa-cium there are 3 large, multiporous pore-chaml)ers. 



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 rhomlnc, 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, 

 which 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 zoa^cia it can be distinctly 

 seen through the frontal wall (fig. 9 a). The operculum (lig. 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 frontal wall of the dis- 

 tal zooccium or in the ooccium-bearing zooecia from the proximal part of the 

 ocEcium. 



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 s])ines. 



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 (iMiss .Jelly). 



' 45, p. 5o. 



