22 JDr. H. Woodicard — Synonymy of Fhilliima gemmnlifera. 



nature) 5 cubic feet of air would be displaced. The grains of sand 

 are very rounded. The proportion of a sphere to its circumsci'ibing 

 cube is '5236, so the interstitial space is rather less in this sand than 

 it would be with an equal mass of small shot of uniform size. Tlie 

 cementing power of moisture in sand is very remarkable, for moist 

 sand will stand nearly vertical for a considerable height, the same 

 material when dry flowing like water. The sand dunes when 

 moist being denuded into cliffs by the sea, but not at other times, 

 show this.' 



Probably I may be asked what is the geological application of the 

 foregoing. Well, I did not write with any special application in view 

 — but simply to record a curious fact. If, however, we substitute 

 beds of rock on a large scale for the sandy laminae, and molten rock 

 injected from below, for the air, we shall have a pretty good model 

 of the modus operandi of the formation of the laccolites or stone 

 cisterns so well expounded by Mr. Gilbert in his Geology of the 

 Henry Mountains. 



YII. — Note on the Synonymy of Phillipsia gemmulifera, Phillips 

 sp. 1836, A Carbonipeeous Tbilobite. 



By Henry "Woodwakd, LL.D., F.E.S. 



ALTHOUGH the Carboniferous Trilobites are but few in number, 

 and are all included in four genera, they have not escaped the 

 usual trouble arising from incorrect determinations. 



One of these occurred in reference to Phillipsia gemmulifera, 

 Phillips, sp., better known by the name of "Phillipsia pustulata," 

 Schlotheim species, a name first applied to this form by Professor 

 de Koninck in 1842-44 (see Descr. Anim. Foss. Terr. Carbonif. de 

 Belgique, p, 603, tab. liii. fig. 5). 



This Trilobite, first known by a pygidium only, was very carefully 

 figured in " Brongniart's and Desmarest's Histoire Naturelle des 

 Crust. Foss. 1823, p. 145, pi. iv. fig. 12, 1822," where it is called 

 " Asaphus " from the black limestone in the environs of Dublin. 



It was next figured by Phillips in his Geology of Yorkshire, 1836, 

 vol. ii. pi. xxii. fig. 11, p. 240, who named it Asaphvs gemmuliferus. 



Buckland again repeats the figure later in the same year, and 

 follows Phillips's name of A. gemmidiferus. 



Prof de Koninck, in 1842-44, changed the name to Phillipsia 

 pnstulnta, quoting Schlotheim's " Nachtrage zur Petrefactenkunde" 

 (ii. Abth. pp. 42-3, Gotha, 1823, and Atlas, p. 22, and plate xxii. 

 fig. 6) as his authority. Now as Schlotheim's Trilobite differs very 

 greatly from Phillips's figure, and also from those given by Brong- 

 niart, and by Buckland, and as moreover Schlotheim's specimen 

 was said to have been derived from the youngest Upper Transitional 

 Limestone (Devonian) of the Eifel, I felt great doubt in accepting 

 Prof, de Koninck's correlation of Phillipsia gemmulifera with the 

 Trilobites pustulatus of Schlotheim. 



1 See ^olian Sandstone, Geol. Mag. 1881, p. 197. 



