REPORT ON THE DIATOM ACE;E. 101 



born-like processes, which are not situated on the protuberances between the two processes, 

 but alternate with them. 



Cerataulus turgidus, Ebrenb., var. polyceros, no v. (Plate XXVI. figs. 6 and 8.) 



The organisms here figured belong to the genus now before us, although the valve is 

 of considerable size, and is distinguished by the presence of some well-defined irregularly 

 scattered granules. That both forms, which were collected in the same locality — the Sea 

 of Japan — represent the same species is unquestionable. 



The general aspect and sigmoid curve of the frustule and connecting zone point to 

 affinities with the Cerataulus turgidus of Ehrenberg. On comparing, however, our two 

 figures with the Cerataulus turgidus of the Typenplatten of ■ Moller, and with the 

 different specimens which we find in the typical preparations of Eulenstein, they agree in 

 all respects, except that Moller's specimen is provided with a remarkable crown of thorns, 

 along with very small irregularly scattered valval thorns, while in the frustules of Eulen- 

 stein's preparation only the very minute thorns occur — differences that are of little 

 moment. In the case of the Challenger forms, on the other hand, the minute thorns are 

 entirely absent ; and, instead of a strong long point or cornu alternating with the two 

 short processes, there is present a group of strong, short obtuse cornua. These marks 

 of distinction have been looked upon as sufficient to justify the establishment of a new 

 variety. 



Biddulphia, Gray. 1 



Although, as above stated, I cannot adopt the view of Professor Smith, according to 

 which he would unite the genus Cerataulus, Ehrenb., to that of Biddulphia, I am of 

 opinion that the union of the genera Zygoceros, Ehrenb., 2 Odontella, Ag., 3 Porpeia, Bailey, 4 

 and Amphitetras, Ehrenb., 5 to that genus as advocated by him is well founded. Thus the 

 only difference of any importance between Zygoceros and Biddulphia is the circumstance 

 that the frustules of the former are isolated. A Biddulphia, however, may also be found 

 solitary, not only as a result of having been casually detached from a series, but because 

 its mode of reproduction supposes that, at some time, the frustule should occur free. 

 Again, only the absence of spines on the margins of the valve distinguishes Odontella 



1 Gray, Nat. Arr. of Brit. Plants. 



2 Compare Zygocerus mobilensis, Bail., Smithson. Contrib., 1859 ; Zygoceros rhombus, Ehrenb., Kreideth., 

 p. 80, N. 61, pi. iv. fig. 11; Kiitz., Baa, pi. xviii. fig. 9; Zygoceros surirella, Ehrenb., Kreideth., loc. cit., 

 fig. 12, Kiitz., loc. cit., fig. 12; Roper, Micr. Journ., voL vii. pi. vi. figs. 11 and 12. 



3 Ag. Consp., 56, Kiitz., Bacill, pi. xviii. fig. 89, pL xxix. figs. 88 and 90 ; Wigand in Hedwigia, vol. ii. 

 p. 45, pi. vii. fig. 21, Montague, SylL, p. 473. 



4 Bailey, MS. Pritchard, op. cit, p. 850, pi. vi. fig. 6. 



5 Ehrenb., Kreideth., p. 62, N. 22 ; Ralfs, Ann. and Mag., vol. xii. pi. viii. fig. 5 ; Smith, Synop. Brit. 

 Diat., vol. ii. p. 47, pL xliv.=fig. 318 ; Jan. et Rabenh., Hondur., p. 4, pi. i. fig. 3 ; Heiberg, Conspec, p. 42, &c 



