ANTHRACOMYA PHILLIPSII. 12] 
Dimensions.—The type specimen, Pl. XVI, fig. 10, measures— 
Greatest diagonal ‘ : . 20 mm. 
Greatest dorso-ventral . 3 Peeler. 
Pl. XVI, fig. 14—Greatest diagonal : : 7 20) mam. 
Greatest dorso-ventral . : = ll saowery 
Lateral , cum 
Localities —Blackband ironstone and shales of the North Staffordshire Coal- 
field, as far down as the Basseymine and the Gubbin ironstone. The Knowles 
ironstone series, North Staffordshire. The Upper Coal-measures of Ardwick, 
Lancashire ; Slade Lane and Bradford, near Manchester. Blackband, Blaina, South 
Wales. Coal-pit, Heath, and black shale, Kingswood deep pit ; Bristol Coal-field ; 
Speedwell pit, Gloucester ; Trafalgar pit, Cinderford, Forest of Dean. 
Observations—The original type of this species was named by Dr. W. C. 
Williamson, who obtained his specimen from the Spirorbis-limestone shale of 
Pendlebury. He described it as ‘‘ delicate, broad, and wide proportionally to its 
length,” and says his specimen resembled that vague shell U. nuciformis, of 
Hibbert, of which all trace has been lost. He states, too, that in this bed the 
shell is always compressed. I am able to figure this shell in Pl. XVI, fig. 10, by 
the kind permission of the authorities of the Manchester Museum, Owens College. 
Phillips, in a letter quoted by Murchison in his ‘ Silurian System,’ p. 88, describes 
four different shells (Unios) as occurring in these beds. One— smooth, tumid, 
with prominent beaks, but with very distinct lines of growth, and rather short, 
straight hinge-lines, looks like a young Modiola; a second form, with nearly 
elliptical hinge-line, deviating considerably from parallelism with the front ends 
in a prominent angle; “lines of growth strong, shell very thin, beaks slightly 
prominent. Mr. Williamson has inaccurately referred this shell to Unio nuci- 
formis. It occurs in the red beds above the limestones, in the black bass and in 
the underlying Coal-measures.” 
A “third species, which I named Unio rugulosus, is of obliquely expanded or 
semi-elliptical form, the hinge-lne forming the diameter [I suppose he means 
when both valves are lying open, flattened out, connected by the hinge]. Surface 
concentrically marked with broken undulations, often showing radiations on the 
posterior slopes ; shell exceedingly thin. Unionidz of the same species occur in 
the bed of mottled marls above the [Spirorbis] limestones, in the black bass or 
shale above the main limestone, and in the shale beneath all the calcareous 
bands.” 
A difficulty at once arises as to which shell Phillips considered identical with 
Williamson’s Unio Phillipsvi. Four forms altogether are described in the letter 
to Sir Roderick Murchison quoted above; the first ‘‘a shell so very like a young 
Modiola,” and three forms referred to Unio. In the remark on the first of these 
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