BY .JOHN MITCH KM.. 



44:5 



Obs. — When describing Hausmannia meridianus (These Pro- 

 ceedings, x., 1895, PI. xxxviii., figs. l-.">, etc.) Mr. Etheridge, 

 Junr., and myself joined with it the present form, under the 

 impression that the differences in their pygidial macros, etc., were 

 insufficient reason for their separation, and were perhaps merely 

 sexual variations. That this latter part of our conclusion is 

 erroneous still remains to be shown, but the acquirement of much 

 additional material of both varieties has proven that the differences 

 between them are greater than was at first recognised by us; and 

 that in one fairly important assumption made by us, we were in 

 error, viz., that when the pygidial border was removed and bore 

 the spine with it, the spinal or mucronal impression left was 

 identical in botli varieties. Further, a careful revision of a very 

 large number of specimens of the two varieties now in my collec- 

 tion, goes to show that they differ from each other in so many 

 respects, that their specific separation is, from my point of view, 

 justified on scientific grounds. The differences between these two 

 Australian forms seem to be quite as numerous and important, as 

 are those between Dalmanites caudatus and D. longicaudatus, and, 

 therefore, the two local forius present equally strong claims for 

 separate specific distinction. The following is a tabulation of the 

 differences between specimens represented on Plate xv., figs. 1 

 and 3 : — 



Tabulation of differences between D. meridianus and D. loomesi 

 in the case of an almost perfect specimen of each, that of 

 D. meridianus being the nearer to maturity. The measure- 

 ments are in millimetres in every case. 



Parts of the fossils 

 contrasted. 



i. Complete form — 

 in) Outline 



Length and width 

 (//) Length from front mar- 

 gin to outer edge of 

 tail border ... 

 (c) Greatest width 



(at the genal angles) 



Character of the 

 parts in 



I>. meridianus. 



Klontrate oval. 



93 mm. 

 53 mm. 



Character of the parts 

 in I>. loomesi. 



Broadly oval. 



83 mm. 

 57 mm. 



