KONGL. SVENSKA VET. AKADEMIENS HANDLINGAR. BAND. 18. N:0 5. 25 



6. Triceratium loeve Cl. N. Sp. 



Triangulär or quadratic, with straight sides and acute not produced angles. The 

 surface perfectly smooth, no structure being visible on balsam-specimens. In F. V. 

 the centre of the valve is elevated, and the angles are produced into processes, forming 

 right angles with the transverse diameter. 



Distance between angles 0,02 — 0,0285 mm. 

 Pl. VI, iig. 70, '"7,, a. S. V., h. F. V. 



Gallapagos Islands (Eugenie Exp.). 



7. Triceratium {productum Grev. var.) Balearicum Cl. et Grun. (in Cl. et Moll. Diat. 



N:o 154—155). 



This form is closely allied to Amphitetras producta Greville and Triceratium An- 

 tillarum Cl. Its outline is 4 — 5 angular, with the angles produced into short processes. 

 The centre of the valve is elevated and by a depression separated from the margins. 

 The structure consists of rounded puncta arranged in lines, radiating from the centre 

 to the angles, about 5 in 0,01 ram. 



Greatest diameter 0,06 — 0,08 mm. 

 Pl. VI, fig. 73, ^''Vi- 



Balearic Islets (Dr. F. Söderlund). 



There can be not doubt that A. producta Grev. (Micr. Journ. II, p. 94, Pl. 9, 

 % 2) and T. Antillarum Cl. (Bih. till K. Sv. Vet.-Ak. Handl. Bd. V, N:o 8, Pl. V, 

 fig. 29) belong to the same species, which seems to be nearly allied also to Amphitetras 

 elegans Grev. from Monterey stone, in which form the depression between the centre 

 and the margins form an inscribed quadrate. 



Allied to these forms seems to be Am. nobilis Grev. (Träns. Micr. Soc. 1865, 

 p. 105, Pl. IX, fig. 27) from the Red Sea. This species is however larger and seems 

 to be only the pentagonal form of Am. antediluviann. It occurs in Rabbnhorst, Alg. 

 Eur. N:o 2264 from Livofno together with Am. antediluviana, and Mr. Kitton informs 

 me that he has found it in samples from Orkney Islands and Southampton; he also 

 remarks that the processes are much exaggerated in Grevilles figure. Another form 

 related to A. antediluviana is A. tesséllata Shadb. (T. M. S. 1854, p. 16, Pl. 1, fig. 11), 

 of which a variety with very coarse cellulation and large processes occurs in Moron 

 Deposit. 



The Triceratium productum Grev. from Barbados Deposit is a quite different form 

 (see T. M. S. 1863, IX, p. 69, Pl. VIII, fig. 9). 



8. Triceratium Gallapagense Cl. N. Sp. 



Triangulär, with acute angles, not provided with processes. Structure: distant 

 puncta, scattered över the disc of the valve, closer near the margins, where they form 



K. Sv. Vet-Ak.id. Handl. Baud. l.s. N:o 6. 4 



