100 THE VOYAGE OF H.M.S. CHALLENGER. 



Hemiaulus glacialis, n. sp. (Plate XXV. fig. 4.) 



Processus laterales elongati truncati, mucronati ; intermedia frustuli inflatione utrinque 

 septata ; granulis perspicuis stipatis. In mari Antarctico. 



Tins valve, which is perfect, is furnished with two long parallel processes, which are 

 truncated at the ends, and upon each of which a well-defined claw-shaped terminal spine 

 projects from the internal part. Between the long processes, and in the centre of the 

 valve, a slight protuberance or swelling occurs, indicating, when seen in profile, that the 

 plane of the valve must be crossed by two septa. This frustule, which has not been 

 hitherto figured, has been named glacialis, on account of its Antarctic habitat. 



Cerataulus, Ehrenb. 



Professor H. L. Smith 1 has united the genera Cerataulus, Odontella, Zygoceros, and 

 others, under the single genus Biddulphia — a circumstance which has rendered the classi- 

 fication much more intricate, and which therefore should not be adopted, notwithstanding 

 the intimate relation that exists between all these organisms. The oval shape of the 

 valves, the alternation of the two sublateral processes, and the strong horn-like spines, 

 in the case of Cerataulus, compared with the disposition of the frustules in zigzag chains, 

 or their adhesion to each other by alternate angles, the elongated and often septate 

 character of the valves, and the presence of subterminal processes in Biddulphia, must be 

 regarded as essential distinctions between the two genera. This view has also been adopted 

 by other naturalists, among whom Dr Eulenstein may be mentioned. This observer, in 

 issuing the first hundred of his typical preparations, gave, under Nos. 9 and 10, Cerataulus 

 Isevis, Ehrenb., 2 and Cerataulus turgidus, Ehrenb., 3 and under No. 11 Biddulphia pidchella, 

 Gray, 4 recognising, as an essential characteristic of Cerataulus, the possession of strong 



1 Pritchard, op. tit., p. 847. The Lens, vol. i. 1872, p. 89. 



2 = GalUonella, sp..1 Bailey, 1842; Sil. Journ., vol. xlii. pi. ii. fig. 8. 



Biddulphia lasvis; Pritchard, op. cit., p. 847, pi. vi. fig. 7; Roper, Micr. Journ., vol. vii. p. 18, pi. ii. 



figs. 24-26. 



Odontella pohjmorpha, Kiitz., Baa, 1844, pi. xxix. fig. 90; Kiitz., Spec. Alg., 1849, p. 136. 



Jsthmia polymorpha, Montagne ) n , ,- -„-... ., ,„, n , OP 



,,, . , ,. ,.- , 7 . } Quoted in Kutz., Spec. Alg., 1849, p. 136. 



Melosira thermahs, Meneghuu J 



a Ehrenberg., Monatsber d. k. Akad. d. Wiss. Berlin, 1843, p. 270; Bailey, 1850, Micr. Obs., pi. ii. figs. 



26 and 27. 



= Biddulphia turgida, Smith, Synop. Brit. Diat., vol. ii. p. 50, pi. lxii. fig. 384; Roper, Micr. Journ., 



vol. vii., p. 17, pi. ii. fig. 23. 



4 Gray, Nat. Arr. of Brit. Plants, vol. i. p. 294; Ralfs, Ann. Nat. Hist, 1843, pi. viii. fig. 3. 



= Conferva biddulphiana, Eng. Bot., 1807, vol. xxv. tab., 1762; Dillwyn, Brit. Conf., 1809, p. 52. 



Diatoma biddulphianum, Ag. Syst. Alg., 1824, p. 5, and Conspec. Crit. Diat., 1830, p. 54. 



Hooker's Brit. Flor., 1833, p. 404; Harvey, Man., 1841, p. 201. 



Biddulphia trilocularis, Kiitz., Baa, 1844, pi. xix. fig. 89, and Spec. Alg., 1849, p. 137. 



Biddulphia quinquelocularis, Kiitz., Baa, 1844, pi. xix. fig. 1, and Spec. Alg., 1849, p. 137. 



Biddulphia septemlocularis, Kiitz., Baa, 1844, pi. xix. fig. 2, and Spec. Alg., 1849, p. 138. 



Biddulphia australis, Mont., PI. CeL de Cuba, 1845, p. 5. 



