192 Proceedings of the Royal Society of Victoria. 



curvature than in the two genera named. Furthermore, the 

 segments are entire, and without grooves, separated by intercostal 

 spaces of greater or less width, and there ai^e no well-marked 

 anterior facets. On these grounds, therefore, I am led to regard 

 the present fossil as more properly appertaining to the Bronteidae, 

 and possibly referable to Bronteus itself. 



Indefinite and broad pleural segments are common to many 

 species of Bronteus., becoming obsolete near the margin of the 

 pygidium. The median appendage, however, connecting the apex 

 of the abbreviated axis with the similar point on the posterior 

 margin of the caudal shield is nearly always present, and 

 generally bifurcate. No better example of such ill-defined pleurae 

 can be adduced than that of B. senescens, Clarke,* although very 

 broad segments are also present in the typical B. flabellifer, 

 Goldf.t Segments of similar width, and equally lacking in 

 definition, may also be seen in B. campanifer., Barrel indeed in 

 some cases they become more like broad flat folds than segments, 

 such as those of B. Laphavii., Whitf.g Another point which 

 must be taken into consideration in attempting to decipher this 

 fossil is the alteration in appearance caused by the successive 

 peeling-oflT of layers of test, the segments becoming fainter and 

 fainter as the process goes on. This may be seen in Barrande's 

 figures of B. palifer, Beyr,|| and B. angusticeps, Barr.^ 



In regarding this pygidium as .that of a Bronteus, there are 

 two negative points that have to be considered. In the first 

 place there is not the slightest trace of the projecting anterior 

 end, or perhaps segment, of the axis, which is usually seen in 

 this genus to protrude beyond the general fore-margin of the 

 shield, although I have previously suggested an explanation of 

 this. In the second place the hinder-margin seems to be 

 emarginate, excentrically in the specimen's present state it is 

 true, but in a position that would, in all probability, represent 

 the middle line of the caudal shield, were it not for the 

 distortion it has underajone. I know of no Brofiteus with such 



* Forty -second Report Trustees State Cab. Nat. Hist. New York for 1888 [1889], p. 4U3. 



+ De Koniiick, Mem. Acad. R. Bruxelles, xiv., 1st pi., f. 1. 



J Syst. Sil. Boheme, I., Atlas t.44, f. 6 and 8. 



§ Geol. Wisconsin, Survey 1873-79, iv., 1882, p. 31U, t. 22, f. 3. 



i; Barrande, loc. at., t. 45, f. 11. f, hoc. cii., t. 45, f. 27. 



