102 



ACMJEA. 



Acmes a pelt a, Esch. 



Fig. 89. 



around the edge and 



pel'-ta, Fig. 89, is more 

 conical and pointed, and the outside of the shell has 



about twenty-five blunt, 

 radiating ribs. The out- 

 side is gray or striped, and 

 is sometimes very beauti- 

 ful; the inside is mainly 

 white, though there is 

 generally a dark thread 

 a brown spot in the center. A 

 strange form is sometimes found in which the early 

 growth of the shell seems to have been formed on a 

 different plan from that of the ordinary specimen, 

 for it is smooth, brown, and has almost perpendicular 

 sides, like a Nacella; after this it suddenly changes 

 to the ordinary form. It is probable that this was 

 caused by a decided change in the abode of the 

 Limpet, perhaps from the sea-weed to the rock. 



A small, black, conical shell, supposed by Carpen- 

 ter to be an abnormal growth of the young of this 

 species, is now known as Acmcea Asmi, Midd. It is 

 usually found living on the shells of the Black Tur- 

 ban. Its length is one-fourth of an inch, while the 

 ordinary shells of pelta are an inch long or more. 



Acmcsa persona, Esch., per-so'-na, is shown in Fig. 

 90. What a variety of names our Limpets offer to us, 

 and how significant they are ! Spec- 

 trum — the spectre, with its pale, 

 ghostly ribs ; patina — the dish or 

 pan, with its saucer-like shell; 

 Fig. 90. scabra — the rough Limpet, with a 



shell like a fine rasp; pelta — the shield; and now, 

 for the last one, persona — the mask. 



