94 AMERICAN MARINE CONCHOLOGY. 
juveniles of C. fornicata, by the examination of numerous speci- 
mens. 
2. OC. uNeuUIFoRMIs, Lamarck. Fig. 190. 
Anim. s. Vert.,- vi. 25. 1819. 
Crepidula plana, Say, Journ. Philad. Acad. Nat. Sci., ii. 226. 1822. 
Shell subovate or quadrilateral, depressed, concave, from gene- 
rally inhabiting the interior of the mouth of univalve shells, sur- 
face wrinkled; white. 
Length 1 to 1.5 inch, breadth .7 to 1 inch. 
This species is generally parasitic on other shells, and prefers 
the interior of Naticas, Busycons, etc., attaching itself just within 
the aperture. It has been supposed by Gray and others that it 
is not a distinct species, but merely the C. fornicata, modified in 
color and form by situation. This idea is incerrect, because I 
have collected C. unguiformis from external surfaces, yet it still 
retains its plain white color, and is always as nearly flat as cir- 
cumstances will permit. 
Inhabits the entire coast. 
3. C. ACULEATA, Gmelin. Fig. 191. 
(Patella.) Syst. Nat., 3693. 1790. 
Shell ovate, laterally incurved at the apex, radiately irregularly 
ribbed, ribs with tubercles or vaulted scales, sometimes growing 
inte short spires; brownish, sometimes rayed, brown within. . 
Southern Coast. 
Family PATELLIDA. 
The limpets have a conical shell with a non-spiral apex, not 
perforated ; muscular impression horse-shoe shaped. The animal 
has a distinct head, furnished with tentacles, bearing eyes at their 
outer bases; foot as large as the margin of the shell; mantle 
plain or fringed. Respiratory organ in the form of one or two 
branchial plumes, lodged in a cervical cavity, or of a series of 
lamelle surrounding the animal between its foot and mantle. 
Mouth armed with a horny upper jaw, and a long ribbon-like 
tongue furnished with numerous teeth. 
The species are very numerous, and distribution universal. 
Genus PATELLA, Linnzus. 
Syst. Nat., edit. x. 780. 1758. 
The shells described under this genus have been assigned, the 
first to the genus Lepeta, the others to Tectura by modern authors, 
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