MARINE DIATOMS OF THE PHILIPPINE ISLANDS 85 



Diameter, 0.170; diameter of umbilicus, 0.0G4 mm. 



There is an evident resemblance between this delicate species and 

 the coarser and much more convex 77. ma.ximus Petit, which may be 

 considered as a variety of 77. radiatus (O'Meara) Grunow, especially 

 as it is figured by Peragallo, Diatomees, France, plate 119bis, figure 6. 



Type.— Cut. No. 43632, U.S.N.M. 



HYALODISCUS STELLIGER Bailey 



(Van Heurck, Synopsis, pi. 84, figs. 1-2; Schmidt, Atlas, pi. 139 fig. 7.) 



An excellent figure of this is also given by Smith (Brit. Diat., pi. 49, 

 fig. 328) under the name Podosira maculata W. Smith. 



HYALODISCUS SUBTILIS Bailey 



(Pritchard, Inf., p. 815, pi. 5, fig. 60; Janisch, Diat., Hond., pi. 1, fig. 16.) 

 Genus HYDROSILICON Brim 



HYDROSILICON RIMOSA (O'Meara) Brun 



(Micro. Journ., 1871, pi. 3, fig. 1; see also Brun, Espec. Nouv., pi. 21, fig. 8.) 

 Genus ISTHMIA Agardh 



ISTHMIA MINIMA Bailey and Harvey 



(H. L. Smith, Type No. 205; Schmidt, Atlas, pi. 136, figs. 4, 8, 9; pi. 145. 

 figs. 1, 9; Walker and Chase, New and Rare Diat., p. 5, pi. 5, fig. 9; Grunow, 

 Diat., Hond., p. 182, pi. 196, figs. 1. a-d; and the rather crude original figure 

 in Wilkes Exped., vol. 17, pi. 9, fig. 11.) 



This form is well illustrated in Schmidt's Atlas, plate 136, figure 8, 

 which he suggests may be a new species. It proves to be only a 

 rather wide variety of the above. Specimens on the H. L. Smith 

 Type slide No. 205, which are uniformly accepted as correctly named 

 I. minima, agree perfectly. It is quite probable that 7. lindigiana 

 Grunow (Diat. Honduras, Monthly Micro. Journ., 1877, pi. 196, fig. 

 1), and 7. capensis Grunow (Monthly Micro. Journ., p. 182) are 

 merely varieties of the same. The latter, Kitton in a footnote sug- 

 gests, may be the above, and it is certain that the figure in Schmidt's 

 Atlas, plates 136 and 145, are not specifically separate, an opinion 

 held by Witt and recorded in plate 145, figure 5. H. L. Smith writes 

 in connection with his above No. 205 that 7. minima Bailey and 

 Harvey equals 7. lindigiana Grunow. Grunow justifies his two spe- 

 cific names by saying that 7. capensis is distinguishable from 7. lindi- 

 giana solely on the grounds of the presence of certain dim club-shaped 

 bodies enclosed within the frustules of the latter. That these are no 

 essential part of the diatom is unquestionable and they may be dropped 

 out of consideration. The only difficulty in the foregoing is that 

 Grunow's figure of 7. lindigiana represent the coarser markings to be 

 truly rectangular and filled with closely set beading and the markings 

 of the girdle to be elongated bars; whereas in 7. minima and in my 



