292 Mr. R. Etheridge, Jun., on the Gasteropoda 



until such time as their internal structure can be studied in 

 conjunction with that of Patella itself. 



Metoptoma pileus, Phillips (p. 224, t. 14. fig. 7). 



This, the type of the genus Metoptoma, is a well-marked 

 form and an almost perfect specimen. The truncated margin 

 is concave, the apex being placed almost vertically above it. 

 The lines of growth are close and thread-like, with stronger 

 undulations here and there. It is the 



Metoptoma pileus, Phillips, loc. cit. 



Patella pileus, De Koninck, Animaux Foss. p. 328, t. 23. fig. 7, a, b. 



Metoptoma pileus, Morris, Cat. Brit. Foss. 1854, 2nd ed. p. 258. 



Metoptoma imbricata, Phillips (p. 224, t. 14. fig. 8). 



The form of this species closely approaches that of the last ; 

 but it may be at once distinguished by the step-like, more or 

 less imbricating, strongly marked concentric ridges. Phillips 

 describes it as conical ; this term, however, can hardly be ap- 

 plied in this case, as the anterior and posterior sides are of 

 different lengths and angles of inclination. It is the 



Metoptoma imbricata, Phillips, loc. cit. 



Patella imbricata, De Koninck, Animaux Foss. p. 329, t. 23 bis, 



fig. 4. 

 Metoptoma imbricata, Morris, Cat. Brit. Foss. 1854, 2nd ed. p. 258. 



Metoptoma elliptica, Phillips (p. 224, t. 14. fig. 9) . 



A very elegantly proportioned shell, and of which Prof. 

 M'Coy has given a full and good description. It may be at 

 once distinguished from both the preceding species by the 

 proximity of the apex to the truncated posterior margin, and, 

 in consequence, the total absence of the almost vertical poste- 

 rior end. The apex is, as M'Coy states, just within the 

 margin, scarcely terminal (as described by Phillips), and cer- 

 tainly not overhanging (as mentioned by De Koninck). It 

 is the 



Metoptoma elliptica, Phillips, loc. cit. 



Patella elliptica, De Koninck, Animaux Fossiles, p. 330, t. 23 bis, 



fig. 3. 

 Metoptoma elliptica, Morris, Cat. Brit. Foss. 1854, 2nd ed. p. 258. 



Metoptoma oblonga, Phillips (p. 224, t. 14. fig. 10). 



This species is founded on a single specimen, an internal 

 cast, showing the muscular scars. It is quite clear the shell 

 possessed strong concentric ridges, like M. imbricata and M. 

 sulcata ; but if the elongated form and slightly concave ante- 

 rior lateral margins are constant, these will suffice to separate 



