170 P. T. CLEVE ON SOME FOSSIL MARINE DIATOMS. 



they are probably short spines or apiculi. A small specimen 

 shows considerable affinity to T. Jensenianum Gran. (A. Schm. 

 Atl., Pi. 77, f. 15-16), but differs from that form by the short 

 veins being more numerous. P1.12, f. 5, a b, 2 ®- 



T. parallelum, Ehr , Grev. Triangular form=T. obtusion, Ehr. ? 

 Cleve, West Ind. Diat., p. 1G (1878). T. parallelum var. trigone, 

 A. Schm., PI. 76, f. 14-17, (1882). Quadrangular form= 

 Amphitetras parallela, Ehr., Mb. (1840). Triceratium parallelum, 

 Grev. T.M.S., xiii., p. 104, PI. 9, f. 22 (1865). Hexagonal form, 

 Grev. I.e., f. 23. Both the triangular and quadrangular forms occur 

 in the " Tegel." The species is found living in the warmer seas, as 

 the Mediterranean, Red Sea, West Indies, Gallopagos Islands, 

 and as fossil in iEgina Moron and San Jeremie, F.K). 



T. tesselatum, Grev. (T.M.S. ix, p. 71, PI. 8, f. 14). This species 

 belongs to a group of Triceratia ; extremely difficult to exactly 

 determine, so many slightly differing forms having been described 

 as distinct species and also imperfectly figured. As my determina- 

 tion may not be perfectly correct, I give a figure of the only 

 specimen I have seen from the Tegel deposit. Distance between 

 the angles, -08 mm. PI. 12, f. 7. 



T. irregulare var. hebetata, Grun. Van Heurck Syn., PI. 

 Ill, f. 10. One specimen closely agreeing with the above figure. 

 The angles and margin show a structural difference when the focus 

 of the objective is altered. This is probably caused by the existence 

 of two differently sculptured layers. In one focus the angles have 

 large cellules, in the other very small ones. I have some doubts 

 as to this form being the true T. irregulare. 



T. trisulcum, Bail, (in Pritch. Inf., p. 854, PI. 8, f. 24, 1861). 

 A. Schm. Atl., PI. 78, f. 5-8. Of this form I have seen several 

 specimens. Distance between the angles 'lO-'lS mm. 



Var. minor, Cleve. Small. Distance beJMeen the angles, # 1 mm. 

 The apices of the angles are more acute than in the larger form. 

 PI. 12, f. 6, *** 



T. nobile (Grev.), CI. Amphitetras nobilis, Grev. T.M.S. xiii, 

 p. 105, PI. 9, f. 27 (1865). One large specimen. Distance be- 

 tween the angles "115 mm., rows of cellules, 4 in *01 mm. A 

 6mall quadrangular specimen agrees well with Amphitetras pro- 

 ducta, Grev., T.M.S. ii., p. 94, Pi. 9, f. 11 (1862) ; not T. 

 production, Grev. (1861), nor T. balearicum, CI. Grun. and green 

 Sv. Vet. Ak. Handl., T. xviii, p. 25, PI. 6, f. 73, 



