CRITICAL BIBLIOGRAPHY. 15 



1839. In 1839 Murchison refers in his ' Silurian System,' p. 88, to a letter 

 from Prof. Phillips, describing three Unios and one modioliform shell from 

 Ardwick, the latter of which he figures, p. 84, fig. c, and gives a woodcut of Unio 

 acuta on p. 105, fig. e, but he does not discuss further the nature of these shells. 

 Prof. Phillips's letter is as follows : — " This is a small shell from the Spirorbis 

 Limestone of Ardwick, and looks so like a young Modiola that I hesitate to call it 

 Unio. Tumid shell with prominent beaks, smooth, but with lines of growth, 

 short straight hinge. In the argillaceous beds associated with the limestones are 

 three Unios. The most common of these is nearly elliptical, hinge-line deviates 

 considerably from parallelism, with front ends in prominent angle, lines of growth 

 strong, shell thin, beaks slightly prominent. Professor Williamson refers this to 

 Unio nuciformis of Hibbert inaccurately. It occurs in red beds, above limestone, 

 black bass, and underlying coal-measures. 



"2nd Sp. — I have named Unio linguiformis (U. Phillips ii of Williamson), 

 transversely elongated, three times as wide as long, hinge-line almost parallel to 

 front lines of growth. Shell fine, thin, smooth. (Black bass.) 



"3rd Sp. — Unio rugulosus, obliquely expanded, in semi-elliptical form, the 

 hinge-line forming the diameter. Surface concentrically marked with broken 

 undulations, showing radiations on posterior slope. Shell very thin, occurring in 

 marls above limestones, black bass, and shale, beneath calcareous bands." 



1833. Davreux, in his ' Essai sur la constitution geognostique de la Province 

 de Liege,' published in 1833, remarks at p. 101, " Les Unios ou Myas, ou peut- 

 etre Linguke, se montre dans un grand nombre de nos Houillieres. . . . Ces 

 bivalves fluviatiles se trouvent toutes en toit des couches, et n'ont jamais un 

 volume tres considerable." He figures — 



Unio acutus, Sow., ") 



e \ pi- v, figs, 3, 4, 8, 



,, antiquus, Sow., ) 



the latter a very characteristic cast of the hinge. 



1834. Prof. Phillips, in his article on " Geology " in the ' Encyclopaedia Metro- 

 politana,' p. 590, speaking of the bands of marine shells in the Lower Coal- 

 measures of Lancashire and Yorkshire, says, " In the midst of this series of 

 Gannister Coal two layers of these shells occur ; one of them about the middle of 

 the series, considerably above the ' Pecten Coal,' and the other near the bottom, 

 considerably below that coal." This paragraph is quoted by Mr. Binney in two 

 papers on the marine shells of the Lower Coal-measures, ' Manchester Geol. Soc. 

 Trans.,' vol. i, p. 82; and vol. ii, p. 75. 



1834 — 1840. Goldfuss published his ' Petrefacta Germanica,' p. 180, during the 

 years 1834 to 1840, and he described and figured (tab. cxxxi) — 



