Mr. T. Davidson on French Liasic Spirifers. 263 



the neighbourhood of Caen. M. de Verneuil has given me spe- 

 cimens lately collected by himself in the Lias of Maranchon 

 (Spain). 



Plate XIV. fig. 14, 15. illustrate two varieties of this species from the 



Lias of the neighbourhood of Caen. 

 Plate XV. fig. 11. A remarkable malformation found by M. Deslong- 



champs, and belonging to his collection. 



2. Spirtfer Walcotti, Sow. 1823. PI. XV. fig. 10. 

 Spirifer Walcotti, Sow. Min. Con. vol. iv. p. 106. pi. 377. f. 12, 

 1823. 



Diagnosis. Shell inequivalve, variable in shape, generally 

 transversely oval, with elevated mesial fold and four lateral 

 rounded plaits on each side corresponding to a sinus and plaits 

 in the large valve ; beak more or less recurved ; area narrow ; 

 deltidium in two pieces ; binge-line shorter than the width of 

 the shell ; surface punctuated and spinose. Length 14, width 18, 

 depth 11 lines. 



Obs. This species is easily distinguished from Sp. rostratus 

 by its well-defined mesial fold and few large lateral plaits. It 

 abounds in the Lias of Avalon in Burgundy, and in many other 

 localities. The largest specimen I have seen was found in En- 

 gland by Mr. Moore ; it measured, length 19, width 24, depth 

 14 lines. 



Plate XV. fig. 10. From the Lias of Avalon. 



3. Spirifer Muxsteri, Dav. 1851. PI. XV. fig. 8, 9. 



Diagnosis. Shell inequivalve, variable in shape, wider than 

 long, mesial fold in smaller valve, acute and elevated, an(J corre- 

 sponding to a deep sinus in larger one, with six or seven acute 

 plaits on each side of the mesial fold and sinus ; beak more or 

 less produced, elevated and recurved, or projected backwards and 

 straight; area large, triangular, with deltidium in two pieces; 

 hinge-line shorter than the width of the shell ; structure punc- 

 tuated and spinose. Length 7, width 11, depth 10 lines. 



Obs. This remarkable species was confounded in 1832 with 

 Sowerby's Sp. octoplicatus, which is a Carboniferous species; it 

 is distinguished from Sp. Walcotti by the form of its beak, area, 

 and the greater number of its plaits ; it is also a much smaller 

 shell, rarely exceeding 7 lines in length and 9 in width : the di- 

 mensions of the area are very variable in this species ; in some 

 specimens it is small, its width not exceeding a fourth of its 

 length, while in other cases the length and width are almost 

 equal. Sp. Miinsteri is not so abundant as Sp. rostratus and 

 Walcotti, but is often met with at Fontaine-etoupe-four near 



