244 CONTRIBUTIONS FROM I Ml. NATIONAL HERBARIUM. 



renb.inpart; Ber. Mead. Wiss. Berl. 1844: 264. 1845 cf.Mikxog.pl. 



• Ehrenb. in part; Ber, Akad. Wiss . Berl [844 $45. 



Ehrenb. in part; Mikrog. pi. 38 /.'. \ A // ' - L864. 



ins. Roj . 9 Edinb. 21: 536. pi. L867, 



ii . Journ 7: 164. 



Of the original genus Pyxidicula Ehrenb. no clear idea can be obtained, as Grevillc 

 points "in." Ehrenberg's < 1 i ; i ^r i » « • — i — '• being equally applicable to any of a half dozen 

 genera and his figures being beyond much question solitary frustulee and vah 

 Gallionella Ehrenb.,* that is, of Melosira ' \j [ndeed, he Bays in his diagm 

 Pyxidicula, " Gallionella divisione spontanea perfecta au( nulla."' The indefinite 

 Pyxidicula was then divided into several genera and subgenera,** namely, Dictyo- 

 pyxis '•• accommodate the forms with smooth cellular valves and Stephanopyxis for 

 those wnli Bpinose cellular valves. The former was loosely formed and included evi- 

 dent example 3 of other genera, especially Melosira and Goscinodiscus, and, as the spines 

 phanopyxis are often obscure, perhaps even wanting, on Bingle valves, membeia 

 phanopyxis would also fall into Dictyopyxis. Stephanopyxis includes in its 

 diagnosis and figures the firsl consistent concept of these diatoms, and as elafo 

 by > rrunow ii is the genus to be preferred. Unfort imately, howe> er, ii was not pub- 

 lished as a -_r « - 1 1 ii — until L846.< Systephania was published as a genus in L845, and is 

 truly identical, its firsl figures cited above being unmistakable examples of Stephan- 

 opyxis; but Systephania has never been taken up by the diatomists and until all 

 diatomaceous genera have been typified there is no knowing but thai there may 1"' an 

 older name. The above is, therefore, retained until it can be considered more crit- 

 ically. The diatom of Donkin's Systephania anglicaJ \- excluded. As Grunow 

 points out the presenl genus is very variable as between Bpecies, different individuals 

 of one species, and even the two valves of one individual, ii being not unusual for one 

 valve to be deeper than the other, to show greater development of spines, etc. The 

 confounding of specimens of the Bpurious genus Xanthiopyxis Ehrenb., with this 

 genus has further complicated the Bubject. 



Stephanopyxis appendicula Ehrenb. Mikrog. pi. 18. f. ■/'. L854. Pritch. Bist. 



[nfus. ed. 1. 826. L861. Schmidt, Atlas pi ISO. f. 18 .'>•. 19,31 ■ L888. 



Wolle, Diat. X. A. pi. 62. f. l : 15. L890. 

 Pyxidicula appendicula Ehrenb. Ber. Akad. Wiss. Berl. 1844: 85, 264. 1845. Kutz. 



Sp. Alg. 22. L849. Weisse, Mel. Biol. Acad. Sci. St. Petersb. 2: 241. pi. t.f. 17. 



1855. 

 Pyxidicula hellenica Ehrenb. Ber. Akad. Wiss. Berl. 1844: 85. l s i">. 

 Pyxidicula apiculata Ehrenb. Ber. Akad. Wiss. Berl. 1844: 85. L845. Kiitz. Bp. 



\Ij. 22. L849. Weisse, Mel. Biol. Acad. Sci. St. Petersb. 2: 241. pi. t.f 16. L855. 

 Stephanopyxis apiculata Ehrenb. Mikrog. pi. 19. f. 1Sb. L854. Pritch. Hist. [nfus. 



ed. I. 826. 1861. De Toni, Syll. Alg.' 2: 1137. 1894. (.run. Denkschr. Akad. 



W'ien 48 : 86. L884. Wolle, Diat. X. A. pi. 62. f. 16. L890. 

 Dictyopyxis hellenica Ehrenb. Mikrog. pi. 19. f. 18a. L854. 



Creswellia turns Arnott; Greg. Trans. Eloy. Soc. Edinb. 21: 538. pi. 14. f 109. L857. 

 Stephanopyxis turris Ralfs in Pritch. Bist. Infus. ed. I. 826. pi. 5. f. : f. L861. (.run. 



Denkschr. Vkad. W'ien 48-': 87. pi. 5.f. : 16 (/. 18 :i doubtful; n.-t /. /.. 

 .1884. De Toni, Syll. Alg. 2: L138. L894. Van Heur. Synop. pi. 83Ur. f. It . 



Edinb. 21: •">:;:. L857. 

 b Ehrenb. [nfus. 165. pi. 10. f. la-f. L8 

 • < i. Gallionella op. cit. pi. 10. f. : 7. 



U;ad. Wiss. Berl. 1844: 262 264, 272. L845. 

 i Op. cit. 1845: 80. L846. 



rt. Journ. Micr. Sci. n. s. 1: [2. pi l.f. / :. L861. 



