68 CARBONIFEROUS LAMELLIBRANCHIATA. 



centre of the inferior border an almost obsolete, broad, shallow constriction is visible. 

 Behind, the shell is gradually compressed, es^DCcially above, and slightly expanded. 



Interior. — The anterior adductor scar is large, marginal, situated just below and 

 in front of the umbones, from which it is separated by a sulcus. The posterior 

 adductor scar is round, and placed high up just below the termination of the hinge- 

 line. In the cast there is an elongate sulcus along the edge, corresponding to a 

 slight thickening in the edge of the shell, and no indications of striation. 



Exterior. — The surface is covered with fine striae and plicse of growth more or 



less parallel to the contour of the shell. 



Dimensions : 



Antero-posteriorly. Dorso-ventrally. Laterally. 



PI. II, fig. 12, measures 19 mm. 10 mm. — 



PI. II, fig. 11 ,, 16 mm. 9 mm. 6-5 mm. 



Locality. — In calcareous bullions in a bed of shale, several yards below the base 

 of the Millstone-grit, Congieton Edge. 



Observations. — I am unable to refer these little shells to any described species, 

 and have therefore described them as new. They come from a bed described by 

 the Geological Survey officers in the Memoir entited ' The Geology of the Coimtry 

 round Stockport, Macclesfield, Congieton, and Leek,' p. 72, where a section is given 

 showing the succession of Millstone-grit, Yoredale beds, and Carboniferous Lime- 

 stone, the quarry being nearer the upper part of the so-called Yoredale beds. The 

 Modioli are associated with a large and typical marine fauna- — -Productus, Chonetes, 

 Orthis, Streptorhynchus, and with other Brachiopods, Lamellibranchs, Gasteropods, 

 and Cephalopods. The species now described apjoroaches M. Macadamii, but is 

 more transverse and tumid, and has a longer hinge-line. 



The two specimens, on which the species is founded, consist of (fig. 12, PL II) a 

 cast of a left valve showing the muscle-scars and contour of the shell with a small 

 portion of the shell below; and (fig. 11, PI. II), a semi-decorticated specimen of 

 both valves which has lost the thin fragile portion of the shell next the posterior 

 superior angle, and therefore at first sight appears to be of different contour from the 

 cast, this being due to an accident in extracting the specimen from the matrix. 



MoDiOLA EMACIATA, de Koninck, 1885. PI. II, fig. 13. 



MoDiOLA EMACIATA, (h Kouitick, 1885. Faune du Calcaire Carbonifere de la 



Belgique (Ann. Musee E. d'Hist. Nat., tome 

 xi), pt. 5, p. 177, pi. xxviii, fig. 25, description 

 '*' by Prof. Jules Fraipont. 



Specific Characters. — Shell small, obliquely U -shaped, rhomboidal, very gibbose. 

 The anterior end is small, anterior superior angle prominent, excavated above by 



