485 MAZATLAN UNIVALVES 



Tlie true M. vitulinus, Lam. appears to be an African shell, 

 closely resembling but distinct from the very variable species 

 of W. America. The Mazatlan specimens are very rarely 

 white, or banded with purple br _>wn ; but almost always of an 

 auburn tint, especially at the border of the mouth, which is 

 white within. Shape generally with the spire moderately 

 elevated, sometimes turrited, sometimes depressed and pyri- 

 form. Upper whirls angular, generally flattened, with regular 

 varical ridges as in Trophon. Nuclear whirls smooth, turrited, 

 iixed slanting, deciduous. Normal whirls scabrous, generally 

 developing a row of obtuse nodules on the shoulder, which some- 

 times elongate into faint costae. Varices foliaceous, extremely 

 irregular, rarely seen on the spire, from one to six on the last 

 whirl, at variable distances. Labiuin smooth, with an infra- 

 sutural tooth as in Pisania. Canal more or less elongate. The 

 creature appears to be of sluggish habits, being frequently 

 worm eaten, and encrusted with Bryozoa, &c. though not with 

 coralline. It is very rarely pierced by Lithophagns and G-as- 

 trochsena. The operculum is diamond-shaped, with two short 

 sides above, and two long ones below, angles rounded : outside 

 with ridges of growth ; inside with a very large muscular scar, 

 reddish, corrugated, with a few lines of growth ; a loose yel- 

 lowish border is seen round the outer edge. The largest sp. 

 measures long. 3*84, long. spir. 1*4, lat. 2*1, div. 60. 



An elevated sp. ,', 3 '84, T9S, 1*8, 40. 

 Apyriformsp. 2*95, '77, 1*7, 80. 



Hob. S. America, Sov^erby, Deshayes. Panama ; under 

 stones, not far from low water mark ; C. B. Adams. Maz- 

 atlan ; not uncommon ; L'pool fy Havre Coll. 



Tablet 2287 contains 4 sp. adolescent. 2288, 3 sp. single 

 varix, depressed. 2289, 3 do. normal. 2290, 2 do. elevated. 

 2291, 3 sp. with 2 varices, depressed. 2292, 2 do. normal. 

 2293, 2 do. elevated. 2294, 3 sp. normal, varices 3 or more. 

 2295, 2 do. elevated varices 3 or 6. 2296, 4 sp. shewing changes 

 of colour. 2297, 3 do. shewing extremes of sculpture. 2298, 

 1 sp. elongated canal. 2299, the largest sp., stout columellar 

 callosity, apparently deposited as a guard against worms. 

 2300, an elongated sp. with a similar callosity. 2301, a sp. with 

 fresh canal, after fracture, bent as in Cassidaria. 2302, a sp. 

 which, in mending a hole between two varices, has protuded a 

 second lip, with a passage to the inside (as in Trochotomus.) 

 2303, 3 separate opercula. The youngest sp. in tablet 2287, 

 and one in tablet 2297 have their opercula in situ. 



