460 MAZATLAN tJNIVALVES 



Mitra lens, Rve. Conch. Ic. pi. 1, f. 1. Mice, in Zeit. f. Mai. 



1851, p. 35, no. 120. C. B. Ad. Pan. Shells, p. 42, no. 17 



H. tf A. Ad. Gen. i. 169. 

 Tiara foraminata, Swains, ms. ; Brod. Proc. Zool. Soc. 1835, 



p. 194. 

 Mitra Dupontii, Kien. Icon. Conch, p. 43, pi. 13, f. 39. 



This species varies very much in growth and sculpture ; but 

 is almost always recognized by the deep punctures which occur 

 at irregular distances in the middle of the whirl, causing tuber- 

 cles to rise up within. Between these are numerous broad 

 costse, 8 13 in a whirl, more or less obsolete in the adult. 

 These are crossed in the young shell, by numerous fine, more 

 or less sharp spiral ridges ; which at varying periods of growth 

 become rounded and finally obsolete. At the same time 

 impressed spiral lines often appear, connecting the pits. When 

 adult, the columella has 3 plaits, with a fourth underneath, 

 rudimentary. In the young shell this is absent ; and the third 

 is often rudimentary, rarely absent. The shell is covered with 

 a smooth, close, dark olive or brownish epidermis ; and is 

 generally densely incrusted with coralline. Underneath it is 

 of an ashy brown, sometimes light, sometimes very dark. The 

 largest sp. measures long. 2*4, long. spir. 1'34, lot. '94, div. 30. 

 A broad sp. 1*35, '65, '6, 50. 



A narrow sp.,, 1*48, '8, *54, 30. 



Hob. Panama, St. Elena, and Is. Plata ; in sandy mud, 

 6 14 fm. ; Cwning. Panama, very rare, C. B. Adams. 

 La Paz, Major Rich. Mazatlan ; not uncommon ; L'pool fy 

 Havre Coll. 



Tablet 2091 contains 4 sp. elongated form. 2092, 5 sp. nor- 

 mal state. 2093, 4 sp. broad. 2094, 7 sp. shewing changes of 

 sculpture. 2095, 2 sp. after acid process, shewing colour. 

 2096, 1 sp. curiously eroded. 2097, 1 sp. with egg-cases. 



Tablet 2098 contains a young specimen, strongly and 

 closely sculptured, but without pits. Deeply cut lines however 

 appear, in which the pits would probably have "afterwards 

 appeared. 



Tablet 2099 contains a small acuminated sp. without pits, 

 costse narrow and distant, spiral sculpture nearly obsolete, 

 columella biplicate. Were it not for the great variation in the 

 ordinary specimens, this would have been regarded as a dis- 

 tinct species. 



