210 MAZATLAN UNIVALVES 
268. AcMEA MITELLA, Wenke. 
Zeit. f. Mal. 1847, p. 187, no. 43. 
= Patella navicula, Rve. Conch. Ic. sp. 130, pl. 40, f. 130, a, 6. 
This shell having been first named from a single worn speci- 
men, the minute details of Menke are not generally applicable. 
The description in the Conch. Ic. applies to a larger number, 
but not to the whole. Shell small, strong, conical, almost 
exactly resembling a common Barbadoes species (?=P. leuco- 
pleura, B. M. Cat. Sagr. Cub. Moll. p. 34, no. 404) ; outside 
either very finely or coarsely ribbed, with or without granules, 
generally eroded or encrusted; inside white, blackish brown, 
tortoiseshell or light chesnut, often with a greenish tinge ; 
margin generally with a row of black dots, more or less con- 
spicuously connected with the apex (especially in young shells), 
sometimes coalescing into a black rim, rarely wholly absent. 
Margin sometimes finely crenulated by the projecting ribs, 
sometimes almost entire. Animal mark irregularly and slightly 
gathered up into points. It either excavates a hollow for itself 
on other shells, or keeps its ground clear while the coralline 
grows up round it. Its small size and shape are not the 
result of the accidents of its position,* as it is generally found 
where it has plenty of room to grow larger if it chooses. 
The smallest specimen measures long. *05, lat. °03, alt. ‘O15. 
A flat 23 oy) 33 "48, 33 "35, 2 pe 
A conical ht x mh eid Oa ee pas Panes ga 
Hab.—Mazatlan, Lieut. Shipley, Mus. Cum. :—do. Melchers, 
Menke :—do,; not uncommon; L’ pool Col. 
Tablet 1010 contains 5 specimens very young.—1011, 17 
young shells, each varying in colour, &c.—1012, 30 specimens, 
of which no two are coloured exactly alike.—1013, 4 specimens 
shewing external variations.— 1014, a specimen in situ on: 
Fissurella ; also Patella discors with attachment marks.—1015, 
a gigantic specimen, if of this species as is probable, measuring 
long. °93, lat. °71, alt. °A41. 
Genus SCUTELLINA, Gray. 
Seutellina, Proc. Zool. Soc. 1847, p. 168, no. 405. 
Scutella, pars, Brod. Proc. Zool. Soc. 1834, p. 47: non Lam. 
Patella, pars, auct. 
* Dr. Gray, when first examining this collection, expressed the opinion that 
P. Mexicana, P. discors, A. mesoleuca, A. fascicularis and A, mitella, might he 
varieties of the same species, according to station, food, &e, 
