162 BULLETIN 100, UNITED STATES NATIONAL MUSEUM 



TR1GONIUM CAELATUM (Janisch) Mann 



(Schmidt, Atlas, pi. 81, fig. 19.) 



De Toni rightly rejects Grove and Sturt's, including this diatom 

 under their T. plenum ( T. weissflogii) , to which it has only the most 

 superficial resemblance. (Syl. Alg., p. 949; Grove and Sturt, Oam. 

 Diat.,p. 328, pi. 11, fig. 22.) 



TRIGONIUM CINNAMOMEUM (Greville) Mann 



(Micro. Journ., 1863, pi. 9, fig. 12; Van Huerck, Synopsis, pi. 126, fig. 1.) 



Grunow 's assignment of this to Cestodiscus, indorsed by Van Huerck, 

 as well as his suggestion that it be put in a new genus, Pseudotricera- 

 tium, favorably mentioned by Van Huerck, are both unsatisfactory. 

 It seems better to accept Greville 's original view, as De Toni does, 

 but to change the wholly untenable name Triceratium into its true 

 correlative, Trigonium, the generic title proposed by Cleve for just 

 such members of Triceratium as this one is. For a full treatment 

 of this question see my Diatoms of the Albatross Voyages, page 292. 



TRIGONIUM CONTUMAX, new species 



Plate 39, fig. 6 



Valve ridgedly triangular, with straight sides and acute angles; 

 central portion slightly depressed below the sides and the even more 

 elevated apices; markings a marginal row of coarse, roundish or 

 square blotches extending into the apices, arranged in well-separated 

 rows i hat are almost perpendicular to the side, but more truly con- 

 tinuous with radii drawn from the center of the valve ; these radii are 

 represented by shining watery lines, running from each row of beads 

 to the center, at which there is a small rosette of similar round or 

 roundish beads ; in side (girdle) view the slight depression of the cen- 

 tral portion of the valve and the very slight elevation of the angles 

 above the sides are clearly seen; the line of demarcation between the 

 girdle and the downward curve of each valve is marked by a narrow 

 sinus or groove running around the frustule ; the girdle is almost hya- 

 line, except for a single row of widely separated beads on its upper 

 and its under edge. 



Diameter, 0.0486-0.0873; lines of beads at margin, 3 in 0.01 mm. 



This diatom has some resemblance to a number of species, particu- 

 larly to T. margaritiferum Cleve (New and Little-known Diat.,p.26, 

 pi. 6, fig. 76), which, however, has concave sides, blunt apices, and no 

 radiating lines. Cleve found it in the Galapagos Islands. It als > 

 somewhat resembles the misnamed figures in Truan and Witt's Dia- 

 toms of Hayti, plate 5, figure 9, and plate 6, figure 16, there called 

 Stictodiscus jolmsonianus Greville. There is indeed a specious resem- 

 blance here to the genus Stictodiscus, (1) because of the watery lines 



