346 



leading characters ; for there is reason to expect, that on the 

 same geological horizon at other points of our Cotteswolds, 

 additional specimens may occur, when their exact localities 

 should be recorded, in order to complete our knowledge of the 

 true range and distribution of the species here introduced. 



SYNONYMS. 

 PUcatula Icevigata, d'Orb. sp. 

 (Gen. Harpax, Parkinson, 1811. Deslongchamps, 1858.) 

 1850. A. d'Orbigny, Plicatmla Icevigata, Prodrome etage liasien, 

 No. 216. 



1857. E. DuMORTiER, PUcatula Icevigata. Notes sur quelques 

 fossiles. Lyon. 1857, p. 5, PI. 2, fig. 2. PL 3, fig. 1, 2, 3. 



1858. J. A. EuDES Deslongchamps, Harpax Terquemi. Essai 

 sur quelques plicatules fossiles. Mem. de la Soc. Linn, 

 de Normandie, Caen, 1858, p. 29—143. PI. 7, fig. 11—15 



1869. E. DuMORTiER, Harpax Icevigatus (d'Orb. sp.) Etudes 

 Palceontologiques (iii^'"^ partie) p. 312, pi. LX, fig. 9 10. 



DESCKIPTION. 



Shell large, ovately oblong, always more or less oblique; 

 attached by umbo of right valve ; test not very thick for its size; 

 surface often in bosses, much depressed. The shell possesses 

 lamellated folds rounded on their edges, the plates overlapping 

 each other so as to leave free, successive zones, of from 2 to 6 

 millimetres in width, bounded by very irregular concentric lines 

 of growth ; these layers easily exfoliate, and it is diflBicult to 

 obtain in a perfect state that part of the shell which is near the 

 umbo ; the part toward the apex of the shell is less rugose, the 

 lines of growth closer, and the contour neater. The apex forms 

 a small triangle, terminating in a very acute angle, which 

 usually, during growth, tends a little to the right; a character 

 rather remarkable in a shell so large, but unfortunately, a 

 character which one has rarely an opportunity of observing. 



It rarely or never preserves a. trace of the body to which it 

 was attached, though specimens have been found in which 



