70 



E. GROVE AND G. STURT ON 



Striated fragments occur occasionally in this deposit, which 

 may be fragments of the discs or connecting membranes of 

 large forms of Coscinodiscus, but at present we are without 

 certain evidence of this. 



Steplianopyxis turris (Grev.), Grun. (Cresivellia, Grev., 

 " G. D. C.," p. 64, PI. 6, Fig. 109 ; also "F. J. L.," p. 36).— Not 

 frequent, but typical. 



St. turris, var. brevispina, Grun. (" F. J. L.," p. 35). — Frequent, 

 usual diam. about , 0016". Length about '0012", with about 10 

 cellules in # 001". Central group of spines very small and 

 short. 



St. (turris, var. ?) valida, Grun. (" F. J. L.," p. 37).— Very 

 common. The most abundant diatom in the deposit. Agrees 

 with Grunow's description, but exceeds the maximum diam. 

 named by him. Valve moderately convex. Diam. from '0025" 

 to , 006". Cellules about 3 in 'OOl". Spines usually conspicuous, 

 curved, and with sharp points, in sub-marginal ring of 10 to 20 

 in number. In some of the larger specimens the spines are small 

 or even wholly wanting, as is the case also in the closed-allied 

 St. superba (Grev.), Grun. (Cresivellia, Grev., " T. M. S.," Vol. ix, 

 PI. 8, Figs. 3, 5). Such large specimens without spines seem to 

 us to be identical with Coscinodiscus splendidus, Grev. (" T. M. S.," 

 Vol. xiii, p. 44, PI. 5, Fig. 3). 



St ferox (Grev.), Grun. {Cresivellia, Grev., " Q. J. M. S.," 

 Vol. vii, p. 166, PI. 8, Figs. 15, 16). — A form agreeing with 

 this is present sparingly ; but as a frustular view shows two 

 dissimilar valves, one of which resembles in all respects those 

 figured by Greville, while the other is much less convex, we 

 cannot consider it as typical. 



St. barbadensis (Grev.), Grun. (Cresivellia, Grev., " T. M. S.," 

 Vol. xiii, p. 3, PI. 1, Fig. 11). — We place here a species which is 

 very abundant in this deposit. Frustular views show a pair of 

 dissimilar valves with broad sutural keels. One valve closely 

 resembles Greville's figure, but the other is less convex, and 

 has numerous spines, which are not curved, and are slightly 

 widened at the ends. The whole frustule bears a resemblance 

 to St. corona, Ehr. ("Van Heurck Syn.," PI. 83 ter., Fig. 11), 

 and we agree with Heir Grunow (" F. J. L.," p. 39) that it is 

 probably a form of that species. Valves '0012* to 0022" diam. 

 One hemispherical, with a circle of 8 to 12 winged acute spines 



