3G0 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



Brcbissonia Gruti. Vcrh. Zool. liot. Gw. Wicn 12: 512. 18(J0. O'Meara, Phk-, 

 Roy. Irish Arad. II. 2: ;^88 (not fig.). 1875. Van ITcur. Treat. Diat. 244. /. 44- 



ISM. 

 CoUctoncma I5n'b. in part; W. Sinilh, Synop. 15rit. Diat. 2: 70. pi. 56./. S; 



onema 



7.f. 4Sa-h. 



ISGl. 



Donjphuru (Kiit/..) W. Sinith, Synop. Brit, Diat. 1: 77. pi. 24- J- ^23. 1853, iii part. 

 Schizoiirvin C. Ag. in part, Tliwaitcri, Ann. Mag. Nat. Hist. IT. 1: 170. pi. 12. f. II. 



1848. Van Ilrur. Synop. pi. 17. f. S, 6. 1881. 

 Berhleya Grev., in part; Scott. Crypt. Fl. 1: 2!)4. 182;i, Ralfs, Ann. :Mag. Nat. 



Hist. 16: 1 10. pi. .?./. 2. 1845. Van ilour. Troat. Diat. 245./. .^fi. 189(1. 

 Aniphiplnira Kiitz. Bacill. lOli. pi. 3.f. f,2. 1844, in part. Van Hour. Synop. 113. 



pi. 17. J. 14-15. 1881. Clove, Sv. Vot. Akad. llandl. 26-: 125. 1894. Van Hour. 



Treat. Diat. 242./. 42. 189G. 

 licit hdiiaX AW Hour. Treat. Diat. 243./. 43. 1890 (V). 

 Navkula Bory, in part; W. Sniilli, Synnp. Brit. Diat. 1: 46. pi IG. f. 129. 1853. 



Kiitz. Bacill. 94. pi. 28. f. 45, pi 30. J. 44. 184-i. Donk. Brit, Diat. 42. pi G.f. 



11-12. 1872. 



m 



Tlii' sepanilioii of tlu^ aoovr gcurni, in wlmlr or in purl, from Ihr truo Navitnla 

 diaton^s in gi^nomlly frit. l>y shhlenls lo be TUH'(\^sary. Altliougli lliry have a navitu- 

 loid<)nt]in(nuul possess valvetslhal arc :ilike;iTi(l that l)ear a ra[)luMlivi(l<Hl at the center, 

 they po?sf^ss sev(Ta. eluiracteristics fountl in no otluM* mivirnloid diatoms. The eliicf 

 diaracterit^tic is the elevated, ridge-like Viorder of silica that surrounds Ihf^ two lialves 

 of the raphe, partly or eompletely inelosint^^ ihcm and, by its longitudinal extension 

 at the eenterof the valve (where h represenis llie eentral nodule), separating the two 

 halves of tlu' raphe fartlu^r and farther, nnlil in Amplupleura and Reielieltia the 

 greater h^igtli of the valve is traversed by tins ridge and ihi' two halves of the raphe 

 are near th(^ apices. It is on the basis of the gradual extension of this ridge and the 

 eouS(^quen1 progressive separation of the l\v<t halves of the rapln- that 1 have here 

 combined these forms into one genus, as it a])pearsto nie th(Te is no distinction between 



the genera above ennmcTated except this variable (nie. Vi(^wed from this stand- 

 point the series would be as follows: (1) Frustulia (=Van Ileurt^kia), where the central 

 extension of the ridge is short and the two halvc^s of th(^ raph(^ trav(^rse nearly the 

 whole length of the valve; (2) Brebissonia (synonyuKjus with Doryphora), Avhere the 

 central extension of the ridge is greater; (3) Berkeleya, where the central extension 

 of the ridge is one-sixth to one-fourth the length of the valve and the two halves of 

 the raphes are correspondingly reduced; (4) Aniphipleura and Keicheltia, inwhicli the 

 central extension of the ridge is extreme and tlu^ two halves of the raphe very short 

 and near the apices. It seems to me simplicity is gained by this union, since one 

 member of the series runs into another, and especially since they are otherwise greatly 

 alike, being characterized by great delicacy of structure Avith transverse beaded 

 striae of extreme fineness covering the entire valve, except the ridge. Reicheltia is 

 the most aberrant of this group, its striae being large, though very finely punctate, 

 and the beaded terminations of the divisions of the raphe b(Mng peculiar. « Still it is 

 80 manifestly a unique species of Aniphipleura that it is difhcult to separate it. 



Pfitzer^ brings out the interesting fact that the aliove differ strikingly from 

 Navienla In internal structure, in the process of fission, and in that of conjugation. 



FrustuUa rhoraboides (Ehrenb.) Do Toni, Syll. Alg. 2: 277. 1891. Cleve, Sv. Vet, 

 Akad. HandL 26-; 122. 1894. 



Navimla rhomboides Ehrenb. Phys. Abh. Akad. Wiss. Berl. 1841: 419. pL S. L f. 

 15, 1843? Kutz. Bacill. 94. j)L 28. /. ^5, ipl, SO, /, U- 1844? W. Smith, 



^Cf. Van Ileur. Treat. Diat. 248./. 43. 1896, 

 ^Hanst. Bot. AbhandL 2: ^-871. 



