REPORT ON THE DIATOMACEJG. 47 



really is, but for a profile of alternating granules belonging to two different valves. More- 

 over, judging from the figure of the zonal side of Terebraria herguelensis, O'Me., we cannot 

 recognise in this type the condition of a frustule "binatcly conjoined." Nor can it be 

 admitted that the so-called Terebraria herguelensis, O'Me., should be classed with Tere- 

 braria barbatle?isis, Grev., and it is not easy to decide to what other genus the form in 

 question should be ascribed, so that, though with reservation, the name given by O'Meara 

 may for the present be retained. 



Terebraria (?) sp. (?) (Plate XXV. fig. 2.) 



This figure represents an organism obtained to the south of Heard Island, which 

 shows seven lines having the appearance of indented lines of suture similar to those which 

 have been observed on the zonal side of Terebraria herguelensis, O'Me. It may be 

 observed that the undulating lines are disposed around corresponding straight lines, and 

 that at each of these regions a solution of continuity takes place as a result of the fitting 

 together of the two valves which seem to alternate with one another as in O'Meara's 

 species. In this figure, too, it is to be noted that the granules or costules which are 

 seen in profile differ greatly in number in the different valves. Yet it cannot be doubted, 

 as some have done, that the striation or the granulation of a frustule, presents within 

 certain limits good characteristic features for diagnostic purposes, although the necessity 

 for exercising caution in generalising on such appearances is at once obvious. This 

 has already been referred to by me in the Transactions of the Pontifical Academy, 1 

 where the fact that other Diatoms, such as Eunotia formica, 2 Ehrenb., have the striae 

 irregularly distributed not only on different frustules, but also on the same valve, has 

 been recorded. Apart, however, from the circumstance of the magnitude of the striaa 

 based upon the comparison of the undulated lines of division with those that are found in 

 Terebraria herguelensis, O'Me., this new type may for the present be named Terebraria, 

 although no specific designation can be given, as the characteristics of the valves have 

 not yet been adequately determined. 



Plate XXV. fig. 1 also represents a series of frustules which, although probably not 

 members of the genus Terebraria, but of the genus Fragilaria, yet exhibit, when seen 

 in the zonal aspect, some relation to the Terebraria herguelensis of O'Meara, although they 

 cannot be regarded as identical with that species. The frustules have evidently been ob- 

 tained at different stages of development. The uppermost in the figure has recently under- 

 gone fissiparous division, but the resulting cellules have not yet become detached, although 

 the margins of the adjoining valves are now clearly indicated by the two transverse 

 central rows of granules. This phase would seem to be a repetition of the condition re- 



1 Atti Aceacl. Pontif. d. nuov. Lincei, vol. xxxi. sect. 6. 



2 Ehrenberg, MikrogeoL, pL iii. iv. fig. 18. 



