Vol. 58.| REFERRED 10 MURCHISONIA AND PLEUROTOMARIA, 319 
of the Devonian. The British species are not fully worked out ; 
but they begin, so far as known, in the Durness Limestone, and 
continue throughout the Ordovician and into the Silurian Period. 
The elongated forms probably have Z. (?) angulocincta and the 
shorter L. borealis, from the Durness Limestone, as their earliest 
representatives. Oyrtostropha ranges from the Bala Formation 
(Ordovician) upward throughout the Silurian Period. 
From what has been said, it is clear that we have no certain 
evidence of the appearance of typical Murchisonie in the British 
Proterozoic rocks, but the genus may have begun in the Wenlock 
Formation and be represented by JZ. (?) dudleyensis (p. 320). Pos- 
sibly some of the forms from the Silurian of Gotland described by 
Lindstrém in his Ornate division may be true Murchisonie; but the 
existence of a slit is not indicated in any of the figures, and Ulrich 
refers them to Lophospira, with the exception of JM. deflewa and 
M.crispa. The latter is represented with an opening in the outer lip, 
which has, however, more the appearance of a sinus thanaslit. As 
before stated (p. 316), the earliest-known British species that exhibits 
a slit is a short form occurring in rocks of Llandeilo age. America 
possesses an older representative of Pleurotomaria showing the shit, 
in Schizolopha textilis, Ulr., which is from the upper part of the 
Trenton Group. So far, no light is thrown on the question as to 
whether Murchisona and Plewrotomaria are derived from the same 
stock ; nor have I yet met with any specimens showing a transition 
from the sinus to the slit. 
Before proceeding to describe the species above mentioned, I 
would like to make two emendations in my last paper. I think 
that the species described as Hormotoma antiqua' should be trans- 
ferred to the genus Ectomaria, the body-whorl being less produced, 
the whorls wider, and the lines of growth more oblique, than is 
usual in Hormotoma. J was previously much impressed by its 
resemblance to H. Nieszkowsku, Schmidt, the type of. the genus 
Ectomaria, but the slight prominence of the keels caused me to 
place it in Hormotoma. <A further examination of the specimen has 
led me, however, to conclude that this may be an accident in the 
manner of preservation, and that the weight of the evidence is in 
favour of its reference to Hctomaria. 
The other correction that I wish to make concerns the locality 
of the specimen ot Hormotoma articulata mentioned on p. 269 (op. 
cit.) as from the ‘ railway-tunnel shale’ of Sedgley. Mr. Madeley 
informs me that the locality should be stated as Dudley. I may also 
mention here that I have seen another example of this species in the 
Nicholl Collection, in the Cardiff Museum, from the Wenlock Beds of 
Garcaed, Usk. 
When I described Ketomaria girvanensis” from rocks of Llandeilo 
[Lapworth] age at Minuntion, I knew of only two specimens in the 
1 Quart. Journ, Geol. Soc. vol. ly (1899) p. 270 & pl. xxii, fig. 9. 
2 Ibid. p. 256. 
