26 CARBONIFEROUS TRILOBITES. 



As the original specimen of A. Elchwaldi cannot be found, and it seems 

 certain that two forms of pygidium have been observed and figured from Russia — 

 one a mucronate and the other a non-mucronate form, it appears to be most 

 satisfactory in every way to adopt the course suggested by von Moller, and give 

 the name of Phillipsia Eickwaldi, Fisher sp.,to the non-mucronate form, and retain 

 for the other the name of Ph. mucronata of M'Coy. 



As, however, it is equally certain from the evidence afforded by a large series 

 of specimens — chiefly from the Scottish Carboniferous series — that there are two 

 forms ^ apparently identical in every respect, save that one has a mucronate and the 

 other a non-mucronate pygidium, it would be better to go a little further and propose 

 to make M'Coy's species mucronata a variety of Phillipsia Elchwaldi^ of Fischer. 



Prof. Traquair retains the generic name of Grijfflthides for his mucronate form 

 on the ground that the lateral glabellal furrows, characteristic of the typical 

 PhillipsicB, are wanting. "We would venture to assert that, although not clearly to 

 be seen in Prof. Traquair's specimens, they are present in all the examples of this 

 species, and that when not visible it is simply due to the state of preservation of the 

 individual specimen. The form is undoubtedly a true Phillipsia ; and, although at 

 first we were unable to see the wisdom of attempting to maintain the two genera, 

 Phillipsia and Griffithides, for these closely related Carboniferous Limestone forms 

 of Trilobites, we are now prepared to maintain them without hesitation, and can 

 point to good characters by which they may be readily distinguished. Of course, 

 when the materials are very fragmentary it is next to impossible to define their 

 place positively, but when once the whole specimen of any one species has been 

 correctly figured (as we hope will be found to be the case in the plates accom- 

 panying this Monograph) a great deal of the difficulty disappears. 



Not having been fortunate enough to see Mr. George Tate's type-specimen of 

 G. (Phillipsia) Farnensis, we must accept as conclusive the opinion of Prof. Tra- 

 quair that this species is only a synonym of Phillipsia mucronata^ M'Coy. We 

 have been favoured with the loan of the type-specimens of M'Coy's G. mesotuher- 

 culatiis, from the Woodwardian Museum, Cambridge, and are satisfied that it is 

 synonymous with his Ph. mucronata. 



7. Phillipsia quadrilimba, Phil., sp. 183G. PL VII, fig. 1. 



AsAPHTJS QUADEiLiMBUS, PliiUips. Geol. Yorks., vol. ii, p. 239, pi. xxii, figs. 1, 2, 



1836. 

 Phillipsia quadrilimba, H. Woodw. Cat. Brit. Foss. Crust., p. 50, 1877. 



Nothing is known of this species save from Prof. Phillips' figure and description, 

 which is here reproduced. I have not svicceeded in tracing the original specimen. 



