170 F. KITTON ON DIATOMACEOUS DEPOSITS FROM JUTLAND. 



This diatom occurs in the Nykjobing deposit only, it resembles 

 T. venulosum, of Greville, in Trans. Mic. Soc, but on careful com- 

 parison it will be found to possess many well marked differences. 



Trochosira (nov. gen., F.K.) — From T/so^o?,awheel, and ^eipa, 

 a chain. Frustules in filaments connected by one or more central 

 processes ; valves discoid, convex, smooth, or faintly striate margins. 



6. T. mirabilis (n. sp., F.K.) — Frustules connected by along spine 

 produced from the centre of the valve ; valves in front view smooth, 

 with a central nodule (base of spine) pi. 14, figs. 8-9, Mors, Nyk- 

 jobing, and Fuur deposits. 



This very singular form requires to be seen in a living state to 

 fully understand its structure. The space between the two oppos- 

 ing valves, and perhaps the whole of the frustule, was covered 

 with a non siliceous investing membrane. 



7. T. spinosus (n. sp., F.K.) — Frustules in filaments connected 

 by five or more short processes ; valves in front view convex ; 

 central portion flat or truncate (a section of valve resembles a short 

 truncated cone), the spines produced from the margin of the central 

 portion ; side view of valve discoid, five or more sub-central nodules 

 (bases of spines), margin faintly marked with short strias (pi. 14, 

 figs. 6-7), associated with the preceding. 



8. Sceptroneis gemmata (Grunow) — Frustules bacillar ; margin 

 with distinct, pearl-like granules connecting zone ; finely punctate ; 

 puncta arranged in longitudinal lines ; valve narrow, gradually 

 tapering to the narrow, rounded apices ; costate costal broad, 

 nearly reaching the centre of valve (pi. 14, figs. 4-5), common in 

 the preceding deposits. 



I have named this species on the authority of the Typen Platte ; it 

 resembles S. caduceus, of Ehr., in its markings, but differs much in 

 the outline of side view. I have seen it forming a short series of 

 five or six frustules. 



The forms described and figured in this and the preceding paper 

 are characteristic of these deposits ; many other species occur in more 

 or less abundance, most of which have been described and figured 

 by various observers as occurring in various fossil deposits or recent 

 material. 



