Terehralula costata. 105 



(without a name, and to which I can find no reference in any 

 author), is a most excellent representation of my shell. 



Under these circumstances, I should not have hesitated in 

 considering this shell the true C. marginatus of most authors, if 

 it were not for the observations on the genus Chiton in the Article 

 Conchology of the Supplement to the Ency. Brit., which is I 

 believe from the pen of Dr. Leach. I there find a shell called 

 C. marg'inatus placed along with C. ruber and cinereus under the 

 section *' Marginal ligament rough;" and another called C. Icevi- 

 gutus in the section " Marginal ligament smooth." Now as there 

 is not perhaps sufficient account of the ligament in any of the 

 descriptions yet published of the true C. marginatus, and little 

 dependence on the strict accuracy of application of the word 

 *' IcevP' to this part, I feel myself bound in deference to the 

 accuracy and opinion of Dr. Leach, to conclude I am still not 

 in possession of the true C. marginatus ', and rather to consider 

 my shell as identical with his C. IcBvigatus: — though as his shell 

 does not appear to have been yet published with any specific 

 character, it would not certainly be advisable to adopt the same 

 name. I have therefore given it one expressive of the most ob- 

 vious peculiarity of its characters. Of course this name must be 

 abandoned, should my shell be satisfactorily identified with the 

 true C. marginatus; and the other synonymes restored.* 



Terebratula, Lamarck, Sowerby. 

 8. Terebratula costata. 



T, testa subtenui, lyraeformi, planiuscula; costis longitudinali^ 

 bus rotundatis scabriusculis pectinata; margine dentato. 

 Icon. Tab. nost. V. f . 8 & 9. Aucta, fig. 9. b. 



* Since writing the above, I am more inclined to believe the preceding- 

 species distinct from the true C. marginatus, by finding in Lamarck no refer- 

 ence under that species to the strikingly characteristic figure of my shell in 

 the Ency. Meth. He adopts the original specific character of Gmelin for his 

 C. marginatus, describing from a shell communicated by Dr. Leach ; and only 

 quotes " Pennant, 4. t. 36. f. 2. and Linn. Trans. 8. p. 2L t. I. f. 2." for his 

 synonymes. 



