(511) 
To determine the age of these boulders, which, as the above list 
shows, are by no means rare near Groningen, all that is known 
about the oceurrence of the characteristic fossils is communicated 
below as completely as possible. 
Phacops elegans Sars and Borck sp. 
Scominm 8, -peo02, 0. Tf 4; TeX ef, 10—12: TE XL, £17, 
is said by Scumpr to oceur in the Raiküll strata and the Estonus- 
zone in Esthonia. It was first found in the oldest of the two zones 
G,, near Wahhoküll in the centre of East-Esthonia, together with 
Strophomena pecten L. and Diplograpsus estonus Schot ; its locality 
in the H-zone is almost straight to the south of it near Törwe in 
the neighbourhood of Talkhof, on the border of Livonia. Complete 
specimens, however, have not been found ; the thorax found here is 
there unknown. 
Most probably P. quadrilineata ANG. Laxpsrröm, 12, p. 43; 17, p. 2; 
is identical with this species; it has been described by the latter 
from the oldest strata of the Upper Silurian formation « and h, near 
Wisby. Moreover Scumipr mentions Farö and Lau there, places which 
according to him belong to his middle and youngest zone in Gothland 
(8, p. 74); this notation borrowed from Lixpsrröm seems to me to 
want confirmation. In Sweden this fossil is also found in Dalarne 
(17, p. 27) and if P. elliptifrons Esmarck must be identified with 
this species (which I cannot state with perfect certainty), in Jemtland 
(29, p. 269) as well. The stage there argues a conclusion in the 
affirmative. This fossil is not known from Scania. On the other hand 
it is found together with Leperditia Hisingeri Scar in Malmö 
in the bay of Christiania, it seems in a corresponding stratum 
(8, p. 74). 
This species is not known in the literature of German boulders, 
though Wicanp makes mention of Phacops Stokes’ Mitxu Epwarps, 
the English fossil, which is most like our species (16, p. 40). The 
illustrations of this fossil found near Rostock in Phacites-sandstone 
prove, however, that this species certainly does not correspond in 
all respects with our specimens. Lhacops prussica Pomprcks, may 
also be taken into consideration but neither the latter is completely 
corresponding with those from Groningen; the rock in which this 
species occurs in East-Prussia, “krystalliner, gelblich-grauer ober- 
silurischer Kalk” would not argue against it (23, p. 19). Roruer 
does not mention our species. 
