210 MAZATLAN UNIVALVES 



268. AcMjEA MiTELLA, Menke. 



Zcit.f. 3fal. 1847, p. 187, no. 43. 



=Patella navicula, Sve. Couch. Ic. sp. 130, pi. 40, f. 130, a, b. 



This sliell 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. Sckjv. Cub. Moll. p. 34, no. 404) ; outside 

 either very finely or coarsely ribbed, %vith or without granules, 

 generally eroded or encrusted ; inside white, blackish brown, 

 tortoisesheU or light chesnut, often ^"ith a greenish tinge ; 

 margin generally with a row of black dots, more or less con- 

 spicuously connected with the apex (especially in yoimg shells), 

 sometimes coalescing into a black run, 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 hoUow 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, led. '03, alt. "015. 



Aflat „ „ „ -45, „ -35, „ -17. 



A conical „ „ „ '51, „ '39, „ *34 



Sab. — Mazatlan, Lieut. Shi2)lci/, Mus. Cum. : — do. Melchers, 



Menke : — do, ; not uncommon ; L'pool Col. 



Tablet 1010 contains 5 specimens very young. — 1011, 17 

 young shells, each var\-ing in colour, &e. — 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. -41. 



Genus SCUTELLINA, Gra>/. 



Scutellina, Proc. Zool. Soc. 1847, p. 168, no. 4^5. 

 Scutella, pars, Brod. Free. Zool. Soc. 1834, x). 47 : non Lam. 

 Patella, pars, auct. 



* Dr. Gray, when first examining this collection, expressed the opinion that 

 P. Mexicana, P. discors, A. mesoleuoa, A. i'ascicularis and A, mitellaj might bo 

 varieties of the same species, according to station, food, &c. 



