94 AMERICAN MARINE CONCHOLOGY. 



juveniles of C.fornicata, by the examination of numerous speci- 

 mens. 



2. C. unguiformis, 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 incorrect, because I 

 have collected G. 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. actjleata, 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 

 into short spires ; brownish, sometimes rayed, brown within. 



Southern Coast. 



Family PATELLID.E. 



The limpets have a conical shell with a non-spiral apex, not 

 perforated ; muscular impression horse-shoe shaped. The animal 

 lias 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 

 lamelhe 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, Linnaeus. 

 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, 



