200 MAZATLAN UNIVALVES . 



Shell extremely large ; white, or of a yellowish or greenish 

 tiage, occasionally orange ; with a broad marginal band of a 

 semidiaphanous hue, very conspicuous in the young shell. 

 Muscular scar in adult raised, irregularly lobed and corrugated. 

 The outside is frequently covered with Alga) and bored by 

 Lithophagi. Its surface is a favourite place of adherence for 

 smaller limpets. In the young sheU may be traced about 10 

 very indistinct principal ribs, with a profusion of radiating 

 lirulas. These however very soon disappear. The youngest 

 ascertamed specimen measures long. 1' 65, lat.l'4i, alt. '42. 



The'largest sp. „ „ 9'2, ,, 6'9, „ 4'5. 



A flatter do. „ „ 9", „ 7'1, „ 3*6. 



Sah. — Mazatlan, Beecheys Voyage. — Do., Menke. — Do. ; 

 abundant, L'pool Sf Havre Coll. — Monterey, Col. Jewett, 

 (Grould ms. : non Nittt.) — Payta, Peru, D' Orhigny. 



Tablet 908 contains 3 young sp. different ages. — 909, 1 sp. 

 finely grown, adolescent, margin flattened.— 910, 1 do. margin 

 sharp, muscular scar thick, brownish red. — 911, the largest sp.> 

 outside riddled by Lithophagi. 



260. Patella pedicctlus, Phil. 



Zeit.f. Mai. 1846, p. 21, no. 8. 



=P. corrugata, Bve. Conch. Ic. sp. 132, pi. 40, f. 132, a, b. (1855.) 

 Comp. P. Araucana, B. M. Cat. B'Orb. Moll. p. 53, (no. 448 : 

 ( = however P. zebrina, var., teste Gray m loco.) 



Shell normally flat, oblong, solid, with 10 stout roimded ribs 

 projecting at the margins, of which 2 are in the axis of length 

 with 4 on each side : ribs and interstices radiately striated : 

 yellowish white, generally with more or less of black or brown 

 tortoise-shell markings within, sometimes with the black be- 

 t«veen the ribs as described by Phil, and Ere. Sometimes the 

 shell is more rounded and the ribs rather angular, in which 

 state it might be taken for the young of P. Mexicana. Occa- 

 sionally a fe-^v other intercalary ribs appear. In a very few 

 unusually large specimens, the ribs are nearly obsolete at the 

 margin and the shell is much lengthened. The body mark 

 varies as usual ; when plain, it is gathered into points as in P. 

 discors. The very young shells appear not to develop the ribs 

 marginally, in which state they might be talcen for the yoimg 

 of P. discors. The stout ribs of the adult shell however bear 

 no analogy willi the very finely marked surface of the latter 

 "vvith its curiously puckered ch'cum-umboual portion. With the 



