GASTEROPODES. 295 



diverging from it to the margin, runs down the middle of each leaf. The 

 whole apparatus is retractile within the body, where the lips of a wide 

 gaping cavity close over it. 



This animal is vernacularly called the Sea Lemon. From simple 

 lemon-yellow it appears greatly diversified with purple patches. Of five 

 specimens taken 6th March, four were of pure lemon-yellow, and the fifth 

 of faint purple, variegating a dingy yellow ground. Of other five taken 

 on March 9. of a different year, some were either of plain lemon-yellow, 

 or variegated with small purple patches. The principal difference among 

 many appearing in nothing but the dimensions, and in the greater or 

 less profusion of purple, for yellow always predominates. The finest are 

 saffron-yellow. All the preceding were above middle size, or extending 

 more than two inches and a half. But the full size of this animal is to 

 be very seldom seen. Its torpid inactivity is surprising ; it scarcely ever 

 moves, and commonly dies very soon in the first vessel to which it has 

 been committed. I have never been able to preserve a specimen any 

 considerable time ; and the artists have seldom procured a sufficient view 

 for satisfactory representation. This seems from their real nature, but it 

 may be also from the force required to detach so large a surface as the 

 sole from rocks or stones. It does not appear that our specimens are 

 smaller than those of foreign countries, as the Abbe" Dicquemare computes 

 the length of specimens on the coast of Havre at five inches. 



The reader will remember what is said of the propagation of the 

 Doris verrucosa in the preceding paragraph, as I have not been so fortu- 

 nate as to discover the real and undoubted distinction. 



PLATE XLII. 



FIG. 4. Doris argo, back. 



5. Belly. 



6. Another larger specimen, back. 



7. Branchial apparatus. 



