MARINE DIATOMS OF THE PHILIPPINE ISLANDS 81 



and "B bdaena"', corners of the rectangular frustule not produced, 

 generally broadly rounded, sometimes sharply angular; sides of the 

 valves marked with vertical rows of beads, continuous with the radi- 

 ating rows of the upper surface, the beads oval or round and punc- 

 tate- girdle covered with rows of beads continuous with those on the 

 surface of the valves and therefore arranged across the girdle, not 

 around it; its beads smaller than those of the valves and always 

 round; the groove across the center of each valve appears in side 



view as a deep notch. _ 



This remarkably formed diatom has unmistakable affinities with 

 BiddulpMa, but is wholly without knobs, horns, or other processes or 

 modifications at the apices of the valves. The type species somewhat 

 su^ests " BiddulpMa balaena" (Trigonium) and the now generally 

 discarded genus Odontella. But its strikingly different front view 

 its deep tranverse groove, and the well-marked central rossette of 

 beads make it impossible to refer this form to any known genus. 



I take pleasure in naming it after my friend and efficient colaborer 

 Mr. Henry W. Henshaw, former chief of the United States Biological 

 Survey. 



HENSHAWIA BIDDULPHIOIDES, new species 



Plate 17, figs. 1, 2 



Characters those of the genus. 



One of the remarkable tilings about this diatom is the apparently 

 haphazard variation in the form of the four corners (apices of the two 

 valves) as seen in the side or girdle view. It is not unlikely that the 

 frustules grow in chains, attached by their corners or by the faces o 

 the valves, although no example of this was actually found But 

 even so, this would not explain the variation of the corners. Usual y 

 they are evenly rounded: sometimes, however all four are sharply 

 angular or pointed, and specimens were found with both corners 

 rounded on one valve and both pointed on the other valve of the 

 same frustule. The depth of the frustule, that is, its height as seen m 

 girdle view, also varies greatly. Generally the frustule, is about as 

 broad as high, that is, its depth equals the length of the valves, but 

 small specimens are occasionally four or more times as high as broad, 

 reminding one of occasional small specimens of BiddulpMa pulchella 

 Gray. Thus a specimen in my collection measures in girdle view 

 0.034 mm. in width and 0.153 mm. in height. 



Length of valve 0.034-0.210; width of valve 0.028-0.039; depth 

 of frusUile 0.084 to 0.190 mm. 



Generally present in Philippine Islands dredgings and m some 



abundant. 



Type.— Cat. No. 43627, U.S.N.M. 



