446 Mr. T. Davidson on Lamarck's species of 



species belonging to the greensand of Mans. M. D'Orbigny ad- 

 mits this species, which he places in his genus Terebratella, and 

 states in vol. iv. p. 116 of his ' Pal. Franc/ that the Terebratula 

 truncata, Sow., 1826, M. C. vi. p. 71. pi. 537. fig. 3, belongs to 

 a distinct species, and not to Terebratula Menardi, Lamk., and 

 to which he gives the new name of Terebratella Asteriana, as he 

 cannot retain the name of Ter. truncata, it having been given by 

 Linnaeus to another shell. There exists however some doubt if 

 on this point M. D'Orbigny's opinion is correct ; the general 

 form in T. Menardi is often, though not always, broader than in 

 our Faringdon specimens, the ribs sharper, and depression of the 

 dorsal valve deeper, and bounded laterally by sharper ridges, 

 lines of growth less strongly marked, mesial longitudinal process 

 on inner side of ventral valve shorter and not so strong. La- 

 marck's specimens do not appear to vary so much in form as our 

 Faringdon specimens, and have a much thinner shell; but on 

 examining with great care a numerous suite of specimens of these 

 species, both in the collection of the British Museum and those 

 collected by myself in both localities, Messrs. Waterhouse, 

 Woodward and myself believe that the species may be the same, 

 and that the greater or less thickness of the shell might arise 

 from the difference of the water in which they lived ; the Fa- 

 ringdon specimens being much worn, so that the plaits must 

 have been much sharper in the living state. 



51. Terebratula decussata, Val. and Lamk. PI. XIV. fig. 51. 



T. testa subpentagona, subconvexa, valva majori canaliculata, striis 

 transversis tenuibus longitudinaliter decussantibus : nate subpro- 

 ducta foramine magno. 



Obs. Lamarck refers to the ' Encyc. Meth/ pi. 245 a, b, c. 

 However, in 1811, before Lamarck, Parkinson described and 

 figured this species in the 3rd vol. of his ' Organic Remains/ 

 pi. 16. fig. 5, under the name of Terebratula coarctata, which name 

 must be preserved to the species, as M. D'Orbigny has done in 

 his ' Prodrome/ vol. i. p. 316, and Lamarck's name placed among 

 the synonyms along with Sowerby's Terebratula reticulata, M. C. 

 tab. 312. fig. 5, 6. The Ter. coarctata is very common in the 

 Forest marble and Bradford clay. The only specimen Lamarck 

 had is in B. Delessert's collection. 



52. Terebratula spinosa, Val. in Lamk. PI. XIV. fig. 52. 



T. testa globosa, dilatata : sulcis parvis spinosis : nate brevissima 

 acuta. 



Obs. This species seems to have been first named by Smith, 

 ( Strata identified by Fossils/ 1816 or 1817. Deshayes and Morris 

 also refer to Knorr, Test. Diluv. It is a well-known inferior 



