MAZATLAN UNIVALVES 199 
tenuissime longitudinaliter granulato-striato, transversim minu- 
tissime corrugato ; areis lateralibus indistinctis ; superficie 
tota valde granulatd, tuberculis spheroidalibus et granulis 
catenatim in lineis a jugo subdivergentibus elegantissime in- 
structa ; mucrone subconspicuo, subcentrali ; intus rosea sew 
alha: marginibus acutis et lobis valvarum non separatis, mag- 
nis, fissura in utroque latere und, lobis angulatis, sinu maximo, 
planato; ad jugum tenuissime corrugatd, ad mucronem lainin- 
até; valvd postict hexagonali, duabus fissuris ad terminum 
divisd ; limbo pallit spiculis erectis translucidis copiose ornato ; 
postice, antice, et ad suturas, spicularuim quasi acicularum cristis 
pulcherrime munito. 
Whether the varied colouring of this shell, its elegant sculp- 
ture, the bird-like form of the medial or hexagonal shape of 
the bifissured terminal valves, or the adornment of the mantle 
with transparent needle-like hairs, rising now in tufts, now in 
irregular crystals, be examined under the microscope, it would 
be difficult to find any shell of such surpassing beauty. Only 
one perfect specimen was found, but fresh valves belonging to 
several other individuals were detected among the Spondylus 
washings. The valves in the same shell greatly differ in colour, 
asin L. albolineatus. The posterior valve is peculiarly exqui- 
site in its form, colour and sculpture. There is considerable 
variation in the size of the tubercles, and in the striation of 
the jugum. The outer margin does not enclose the plates of 
insertion, as it does in Lepidopleurus. Long. ‘16, lat. °06, alt. *02. 
Hah.—Mazatlan ; off Spondylus calcifer; extremely rare ; 
LP’pool Col. 
Tablet 907 contains the perfect specimen and 4 valves. 
Famity PATELLID. 
Genus PATELLA, Linn. 
As the shells in this genus can scarcely be distinguished 
from those of Acmza, the location of many of the following 
species in this and the next family is doubtful. 
259. Paretta Mexicana, Brod. & Sow. 
Zool. Journ. vol. iv, p. 369.—Menke in Zeit. f. Mal. 1851, p. 37, 
no. 132. 
= Lottia gigantea, B. M.: Gould ms. 
= Patella maxima, B. M. Cat. D’ Orb. Moll. p. 53, no. 449, 
