350 MAZATLAN UNIVALVES 



very much more common than L. aspera at Mazatlan ; very 

 young specimens of the latter being so rare that I am unable 

 to state their exact difference, and some in each series may be 

 wrongly placed. The ordinary specimens however are dis- 

 tinguished by the flattened form, and faint sculpture. The 

 adults have a very different aspect from each other, although 

 worn specimens may be confounded. It presents less variation 

 of form than either of the other species ; making up for this 

 by the multiform patterns of the stripes. The operculum 

 closely resembles that of L. aspera ; but appears to differ in 

 being more transparent, with the shagreening on the muscular 

 scar less and the spiral strige more conspicuous, and the nucleus 

 less raised and displaying the spiral element. The ordinary 

 size is "4 by '28 ; the smallest is "18 by * 12 ; an extraordinarily 

 large one measures long. '6, long. &pir. '3, lat. '35, div. 50. 



Hab. Mazatlan ; common ; L'pool fy Havre Coll. 



Tablet 1671 contains 7 sp. ventricose, resembling the young 

 of L. aspera. 1672, 8 sp. highly coloured, as in L. aspera, jun., 

 but of normal shape : in the youngest, the stripes coalesce and 

 nearly cover the shell. 



Tablet 1673 contains 7 sp. stripes broad, zig-zag. 1674, 8 do. 

 stripes narrower, hue olivaceous. 1675, 8 do. stripes inter- 

 rupted in the middle. 1676, 7 do. stripes zig-zag at base. - 

 1677, 7 sp. lines very fine, olivaceous. 1678, 7 sp. stripes not 

 interrupted, broad. 1679, 7 do. narrower. 1680, 7 do. very 

 narrow. 1681, 7 do. olivaceous. 1682, 5 do. stripes broken-up 

 into tesselations. 1683, 6 do. markings extremely faint. 

 1684, 7 sp. spire elevated. 1685, 9 separate opercula (others 

 in the shells.) 



399. LITORINA , sp. ind. 



Tablet 1686 contains 2 sp., one young and fresh, the other 

 adult and dead, differing from the rest in colour, which is of a 

 nearly uniform blackish brown, with faint spiral lines of white ; 

 in texture, which is nearly smooth, with a very few extremely 

 1 spiral lines near the base ; and in the columella, which is 

 not excavated. Long. *5, long. spir. '25, lat. '32, div. 50. 



Hab. Mazatlan ; extremely rare ; IS pool Col. 



The same tablet also contains a very young shell, measuring 

 '07 by "05, more obtuse than the young of the other species. 



