170 BULLETIN 100, UNITED STATES NATIONAL MUSEUM 



TRIGONIUM LATUM (Greville) Mann 



(Micro. Journ., 1865, pi. 9, fig. 20; Schmidt, Atlas, pi. 77, figs. 38-39.) 



This species is quite variable. An unimportant variety, despite 

 its assertive name, is Grunow's T. dissimile[m Schmidt, Atlas, plate 

 81, figure 5. So also another form found at the Philippine Islands 

 and named T. zonulatum Greville in Schmidt's Atlas, plate 77, figure 

 33. It may be added that varieties of these two do approach 

 closely. 



TRIGONIUM MEMBRANACEUM (Cleve) Mann 



(Cleve, W. I. Diat., p. 20, pi. 5, fig. 33; Peragallo, Diat., France, pi. 105, figs. 

 4-5.) 



This species could be classified as a small and very delicate variety 

 of Trigonium balaena (Ehrenberg) Cleve, which see. But in addition 

 to its much more fragile structure, the minute beading of its valves 

 is made up of closely set circular beads, so spaced as to produce a 

 quincunx pattern ; while those of T. halaena are set in more widely 

 spaced rows and are oval. De Toni and others unite this with 

 B. titania Grunow, the type figure of which is given in Van Heurck's 

 Synopsis, plate 95bis, figures 6-9, from which it differs in the char- 

 acter of its girdle and in the absence of the remarkable curved row 

 of prominent beads marking the valve at either end of the oval of 

 B. titania. These curious markings favor the idea of placing 

 B. titania in the genus Janischia. My Philippine specimens are 

 unique in being three- angled instead of two-angled. 



TRIGONIUM MULTIPLEX (Janisch) Mann 



(Schmidt, Atlas, pi. 75, fig, 1.) 



For a discussion of the essential unity of this and T. eulensteinii 

 (Grunow) Mann, see the latter. 



TRIGONIUM PARDUS (A. Schmidt) Mann 



(Schmidt, Atlas, pi. 79, fig. 15.) 



Rather close to T. punctatum. Schmidt's type came from N. 

 Celebes. 



TRIGONIUM PUNCTATUM (Brightwell) Mann 



(Micro. Journ., 1856, pi. 17, fig. 18; Schmidt, Atlas, pi. 76, figs. 19-20; pi. 81, 

 figs. 6-7.) 



That this is only a variety of the earlier named T. sculptum Shad- 

 bolt is discussed in my Diatoms of the Albatross Voyages, page 295. 

 It is rather common in the Philippine Islands dredgings and is named 

 separately merely for convenience of reference, a plan here adopted 

 in other similar cases. 



