( 321 ) 



occiuTcnce, wliicli ped'ographically resembles the lilliogmpliical one 

 and probably is of the same age as the Wesenbergen stratum. In 

 this stone a petrifaction is hardly ever found. 



Consequently it takes a long time to gather a collection in wiiicJi 

 the different divisions of Under-Silurian stone are clearly represented. 

 I did not succeed in composing such a collection from the Hcuielum 

 loam-pit. This is partly owing to the fact that this opporiunity to 

 gather erratics existed oidy a short tiuie. The boulder clay proving 

 unfit for use in brick-worlvs,' digging has been left off. 



The principal cause is, however, that boulder clay used to lie dug 

 there in the beginning of winter, and that in the latter part of that 

 season the erratics found were broken to pieces for macadamizing 

 roads, whilst in this very part of the year neither my occupations 

 nor the weather allow of my making excursions. 



The erratic I am going to treat of, was found by me in the 

 Hemelum loampit a few years ago; it may undoubtedly be ranged 

 under the Coratopyge-zone, the eldest r>f the Under-Silurian kinds. 



It contained a kernel of compact, splintery limestone, of a ligiit- 

 grey, more or less greenish colour. This kernel was surroun<led by 

 a yellow-brown, softer crust, caused by corrosion, which was coloured 

 greyish at the surface. Occasionally I distinguished small glauconite- 

 and pyrite-grains. 



When I broke it to pieces, the kernel naturally did not give me 

 any fossils; I succeeded, however, in exposing to view, from the 

 corrosion-crust, the following fossils: 



1. Ceri(toj)ii<i(' forjicula Sars ^). Of this si)ecies I fouiid a head- 

 midshell, a free cheek and three fragments of [)ygi(lium. These 

 remains come from the variety acicularis Sars et Boeck, the axis of 

 the pygidium consisting of 6 segments. The liead-midshell, too, bears 

 more resemblance to fig. 15 than to fig. 17. 



2. Si/mph]/surus- anr/astatus Sars et Boeck '■'). One glabella and 

 three small pygidia were found. In (he latter i( becomes quite 

 clear that as a rule the axis may be clearly distinguished only in 

 stone-kernels. 



3. HoIouKito/yas {/) elatlfron.s Aug -). Numerous more or less unin- 

 jured head-midshells presented themselves. Only in one specimen, 

 one side of wliicli is slill in the stone, the prick in which the glabella 

 ends towards the I)ack is visible. 



1) Broggeh, Die siluiisclien Etagen !2 und 3. p. 123. Tab. III. tig. 15—22. 



2) Brögger loc. cit. p. GO. Tab. III. fig. 9, 10, 11. 

 ») Bröggeh loc. cil. p. 128. Tab. III. lig. 13. 



