MASTOGLOIA. 1 55 



M. exigua Lewis. (Notes on new and rare spec, 1861, pi. 2, 

 f. 5 ; H.V.H. Atl., pi. 4, f. 25, 26* ; Type No. 50), plate 2, fig. 63. 



Valves lanceolate, sometimes slightly produced, sub rostrate ; loculi very 

 few (often only 3), with rounded outline ; strios slightly radiate, 20 in 1 c.d.m. 

 Length, 25 to 3-5 c.d.m. 



Brackish water. Rare? Blankenberghe, Antwerp (Scheldt, dry dock), H.V.H. England 

 (H.V.H., Type 50). 



M. Closeii O'Meara. (Irish Diat., p. 326, pi. 29, f. 10*) plate 25, 



fig. 701. 



Valve elliptical, sub-rhomboid, with apices slightly acute ; raphe straight, 

 with very narrow hyaline area. Loculi, 5 ; the three central ones rounded, large ; 

 the two terminal elongated, abruptly attenuate. Striae rather fine, very radiate, 

 convergent, reaching the raphe. Length of valve, 4^5 c.d.m. ; breadth, 

 2 c.d.m. 



Marine and brackish water. Ireland (O'Meara). 



2. Valve linear-elliptic, with loculi arranged in a straight row. 



M. Dansei Thwaites. ! (w. Sm., s.B.D. i., pi. 62, f. 388; 



H.V.H. Atl., pi. 4, f. 18*; in Types Nos. 46 and 47 Var. elliptica in 

 Types No. 103 and 106), plate 2, fig. 64. 



Valve linear, elliptical, with apices slightly produced, broadly rounded ; 

 loculi 8 to 20, in a straight line ; central nodule surrounded by a considerable 

 hyaline area; stria? bent, radiate, finely punctate, 15 in 1 c.d.m. ; the central 

 ones rather more distant. Length, 3 to 5 c.d.m. 



Fresh and brackish water Blankenberghe (H.V.H.), Heyst (Debv), Bergh (Del.), Aid. Liege. 

 (DeWild.), England (Kitton), Ireland. 



Var. elliptica. (M. [Frustulia] elliptica, C. Ag.), differs from the 

 type form by the inflated elliptical form of the valve. 



M. Grevillei W. Sm. (w. Sm., s.B.D. i., p. 65, pi. 62, f. 389, 

 H.V.H. Atl., pi. 4, f. 20*, Type No. 48), plate 2, fig. 65. 



Valve linear with apices cuneate, obtuse; loculi 15 to 20; central 

 nodule surrounded by a hyaline area; stria? about 10 in 1 c.d.m. radiate, 

 robust and with strong puncta, the central more distant. Length 3-5 to 

 5 c.d.m. 



Fresh water. Ard. Liege. (De Wild). England (W, Sm, !), Ireland, Denmark, Sweden, &c. 



