44 



RELATIVE DEPTII OF TUE SEPTy\ 



In my descriptions of Licmophorae I have introduced the direct 

 measurement of the depth of the septa taken from the summit of the 

 valve to the inner margin of the septum or, in the girdle face, from 

 the upper margin of the frustale to the septa! puncta. The absolutc 

 value of this measure does not however represent the real degree 

 of the deepness of the septa in a given species : they can be abso- 

 lutly deep, as in L. araphidiea, where they have a length of 0.0143 

 mm., more than those of /.. profundcsepiata, which are only 0.0 io5 

 mm. deep and stili relati vely to the size of the frustule they are 

 shallow in /.. araphidiea while in L. profundeseptata they are very 

 deep. It is therefore necessary to take this character not in its ab- 

 solutc value but in its relation to a uniform size of the frustules. 

 The following table (bascd on more than two thousands measure- 

 ments) shows the relative depth of the septa of different species, the 

 size of each species being supposed equal to o.i mm. AH septa 

 below 0.008 mm. can be regarded as shallow, ali above 0.008 (inclu- 

 sive) - as deep. 



L. siihundiiìala Mer. 



L. per magna Mer. . 



L. elegans Mer. 



L. Jiirgensii Ag. 



L. remnloides Mer. . 



L. angli si aia Gr. 



L. infiala Mer. 



L. bastata Mer. 



L. araphidiea Mer. . 



L. dalmatica var. parva A 



L. Reichardti Gr. 



L. capensis Gr. 



L. Ehrenbergii (Kz.) Gr 



L. membranacea Mer. 



L. debilis (Kz.) Gr. . 



0.00 1:) mm. 



0.0028 » 



o.oo33 » 



o.oo33 » 



o.oo38 ji 



0.0040 » 



0.0042 » 



0.0043 i> 



0.0044 '> 



0.0047 » 



0.0048 j) 



0.0049 " 



0.0064 * 



0.0059 » 



0.00Ò2 » 



