654 Mr. T. H. Withers on 
slightly near the inner margin, to fit under the inturned 
margins of the plates of the right-hand series, thus forming 
a kind of hinge (see Pl. X. fig. 4). In consequence of the 
tapering of the shell at each extremity, the plates vary some- 
what in shape according to their position in the shell, but 
there is also much difference in the shape of the plates, 
their number, and ornament, in the different species, On 
the inner surface of each plate of the two columns, near the 
middle, there is a well-marked sub-cirecular muscle-scar. 
Genotype.—L. jamesi (Hall & Whitfield). 
Lepidocoleus graye, sp.n. (PI. X. figs. 1-5.) 
1908. Annelidan Tube (?), Cowper Reed, Geol. Mag. dec. v. vol. v. 
p- 295, pl. xii. figs. 9, 10. 
Diagnosis. —A Lepidoco’eus with more than 16 plates in 
a column, a length of more than 25 mm., and a breadth of 
5 mm.; plates overlapping to almost half their length, 
mostly about twice as wide as long. with an ornament of 
comparatively wide-spaced growth-ridges, about four to a 
millimetre, and of five to six very slightly finer ridges 
between each main ridge, giving the surface, where well- 
preserved, an exceedingly closely and regularly ridged 
appearance. 
Horizon and locality —Upper Ordovician, Lower Ard- 
millan series, Druwmuck group, Mudstones: Thraive Glen, 
Girvan, Ayrshire. 
Collection.—Geological Department of the British Museum 
(Mrs. Robt. Gray Coll.), registered In. 21648 and In. 21649. 
Holotype. — The specimen (In. 21648) figured, Pl. X. 
figs. 1-4, which is presumably the specimen partly figured 
by Cowper Reed (1908, figs. 9, 10). 
Material.—Two incomplete shells with the plates very little 
displaced. 
Description—One specimen (Pl. X. fig. 5) represents a 
shell, including the basal extremity; its length is 20°4 mm., 
and its greatest breadth 5°0 mm. This shell is bent or 
humped, with the result that the plates are somewhat tele- 
scoped and displaced; the shell-layer of the plates has been 
removed in places, so that only the impression remains. 
At least sixteen plates or their impressions can be counted 
in serial order, but, owing to the bad preservation, the form 
of the plate at the base cannot be made out, although the 
rounded shiny impression on the matrix leaves no doubt 
that this really is the rounded basal extremity. Both this 
