434 PATELLIDiE. 



bran chise forming a pectinated plume lodged in a cervical 

 cavity ; foot large, ovate, with plain sides ; buccal mass 

 with cartilaginous jaws; lingual ribband long, copiously 

 armed with teeth, three of which are borne obliquely on 

 each half of each transverse series, the two halves forming 

 distinct squares. 



This excellent genus was founded by Eschscholtz in 

 1833, with a full understanding of both animal and shell. 

 The latter can with difficulty be distinguished from that 

 of Patella, an absence of a nacreous gloss on the upper 

 surface being the chief difference. The group was consti- 

 tuted by several authors almost simultaneously, so that it 

 becomes difficult to determine whose name has priority. 

 It appears to have been first indicated (but without a 

 definition) under the name of Tectum by Audouin and 

 Milne Edwards, who observed that the so-called Patella 

 virginea had an animal presenting peculiarities of generic 

 value at least. The ill-chosen name Patelloidea was given 

 to it by Quoy and Gaimard, and Lottia by J. E. Gray. 



Several species of Acmaa occur in both hemispheres. 

 Some of them inhabit water of considerable depth. 



A. testudinalis, Midler. 



Variegated with brown and white ; spatula-mark more or less 

 painted with brown. 



Plate LXII. fig. 8, 9, and (Animal) Plate A A, fig. 2. 



Patella testudinaria, Mullkr, Prodr. Zool. Dan. p. 237.— Gmel. Syst. Nat 

 p. 3717 (var. Norveg.) 



„ testudinalis, Muli.er, Prodrom. Z. D. p. 237, No. 2872. — Brit. Mar. 

 Conch, p. 131. — 0. Fabric. Fauna Greenland, p. 38.5. — 

 Bosc, H. N. des Coquil. vol. iii. p. 216. — Dili.w. Recent 

 Shells, vol. ii. p. 104.5. —Wood, Index Testae, pi. 37, f. 

 63. — Desh. Lam. Anim. s. Vert. vol. vii. p. .513. 



„ tessellata, Muller, Zool. Dan. No. 2868 (teste Beck). 



