ANTHRACOMYA PHILLIPSIT. 121 



Dimensions. — The type specimen, PI. XVI, fig. 10, measures — 



Greatest diagonal . . .20 mm. 



Greatest dorso- ventral . . .12 mm. 



PL XVI, fig. 1-4 — Greatest diagonal . . .20 mm. 



Greatest dorso-ventral . . .11 mm. 



Lateral . . . 8 mm. 



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 TJ. 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 PI. 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, bat 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 TJnio 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 TJnio rugulosus, is of obliquely expanded or 

 semi-elliptical form, the hinge-line 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. Unionidse 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 TJnio Phillijpsii. 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 TJnio. In the remark on the first of these 



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