DOUBTFUL SPECIES. 181 
the Lower-Ludlow strata of Leintwardine, and the originals were stated to be in 
the Ludlow Museum, but they cannot now be found. I had been in correspond- 
ence with Dr. Holl shortly before his death respecting these types, and, acting on 
a suggestion made by him, I examined, by the kind permission of Prof. Boyd 
Dawkins, F.R.S., the Lightbody collection, now in the Museum of Owens College, 
Manchester, but without meeting with them. Their loss is the more to be 
regretted since no other specimens corresponding with Dr. Holl’s descriptions 
have been discovered, and his species will therefore lapse. It seems to me pro- 
bable that Protospongia Ludensis may have belonged to the genus Dictyophyton, and 
P. maculeformis to Phormosella. 
67. Ponvittus THomsontr, Carter. 
1878. Annals and Mag. Nat. Hist., ser. 5, vol. i, p. 137, pl. x, figs. 1—6. 
I am indebted to Mr. James Thomson, F.G.S., for the opportunity of examining 
the type forms of this new genus and species. The specimens are bi-convex or 
plano-conyex discs with occasionally a depression on one or both surfaces. They 
are composed of rounded or amorphous grains of calcite, from 1 to 3 mm. each 
in diameter, closely aggregated together, so that in a section but little more than 
the partition line between the individual grains is visible. In some cases the 
grains are separated by rock matrix from each other. There are no traces of 
Sponge-fibres of any kind nor of canals. The constituent grains of calcite in part 
exhibit an acicular or fibrous crystalline structure, which is regarded by Mr. Carter 
as indicating acerate Sponge-spicules (loc. cit., pl. x, fig. 4). 
Further, the objects represented as ‘‘ broken ends of the spicules projecting 
from the surface of the large excavation” in the type-specimen appear to me to 
be punctures ina fragment of the shell of some Brachiopod (/. c., pl. x, fig. 6). 
The acerate spicule, figured as the staple form of a perfect spicule (/. ¢., pl. x, 
fig. 5), is derived from the sandy material of the rock matrix, and there is no 
evidence beyond its position that it had any relation to the supposed Sponge. 
These bodies in my opinion are merely nodules of inorganic origin. They are 
from Carboniferous Limestones at Arbigland, near Dumfries. 
68. ScypHta TuBERCULATA, King. 
1850. Mon. Permian Foss., Pal. Soc., vol. iv, p. 12, pl. ii, figs. 1, 2. 
The type-specimen, now in the Museum of Queen’s College, Galway, is a 
fragment of a cylindrical body, with a hollow axial tube and lateral tubes partly 
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