344 AMERICAN JOURNAL 



Of course, neither Gray nor Sowerby were aware of trie char- 

 acters of this species ; and (Acmsea not being then known in 

 the West of Europe) Loitia, as well as Tectum and Patelloidea, 

 simply meant a limpet with a single neck-plumed gill. It 

 happens, however, (according to Woodward in litt.,) that 

 Acmsea was first described in the Appendix to "Kotzebue's 

 Voyage," some years before the Zool. Atlas, and anteriorly to 

 all the Western names. All the rest of the Lottise thus be- 

 coming Acmsea, there remains this one for which the name 

 may be retained. Perhaps other species now reckoned as 

 Acmsea or Patella may prove to be congeneric. The above 

 diagnosis of the animal only applies to this species ; the main 

 point of difference is supposed to be the interruption of the 

 fringe in front. In general characters, Dr. Alcock regards it 

 as more nearly allied to Acmsea; but in special points, in- 

 cluding the character of the teeth, to Scurria. As I believe 

 no Latin diagnosis has ever been written of the species, I 

 have endeavored to prepare one that shall embrace all the 

 specimens I have examined. 



Lottia gigantea is an excellent test for ascertaining the 

 amount of variation allowed in a limpet, inasmuch as there is 

 no other species that offers any approach to it; and the gene- 

 ral habit is so much the same in all the specimens, that no 

 one who examines a large number, would doubt their identity. 

 And yet, in about 30 specimens examined, the ratio of the an- 

 terior portion in front of the apex to the entire length (which 

 is generally a nearly constant quantity in each species) was 

 found to vary from 1 : 7 to 1 : 20. 



The adult is, in shape, something like an enormous Acmsea 

 persona, and calls to mind Helcion pectinatus (of which the 

 animal is not known) and the Southern Patellse of the type of 

 senea, Mart. The color of the interior resembles that of the 

 Cape species, P. petasus, and its congeners. It is generally 

 very brilliant; the body-mark being spotted in clouds with 

 bright sienna, over which more or less of white porcelain is 

 deposited. The shell outside is almost alwaj^s eroded, and of 

 a spongy texture. When perfect, it displays very faint, swell- 

 ing, irregular riblets, which are broad and more or less warty, 

 except on the head ; the warts are very stout in the young 

 shell. The outer margin of well-grown specimens is colored 

 like A.pelta. Sometimes the profile presents an elegant curve, 

 concave anteriorly, convex posteriorly; but often the eroded 

 apex descends almost perpendicularly to the margin. The 

 horny nucleus is very small in proportion, with the apex 

 raised as compared with the adult: in this respect the reverse 

 of the Acmsese. The point is very obtuse, and displays a 

 spongy decollation as in the adult. When less than the tenth 



