APPENDIX. 517 



8-10 cirrhi. The colours described are those of the animals 

 examined; they vary greatly, and in individuals exhibit all 

 the shades of red, pink, purple, brown, maroon, bistre-yellow, 

 and all the greens. 



The foot is long and narrow, with a tumid aspect on the 

 upper surface, rounded in front, without a trace of auricles, 

 obtusely lanceolate at the posteal end, and marked above 

 with red-brown, zebra-like, or narrow, longitudinal, wavy 

 lines; the sole is yellow, having a central depressed line 

 throughout its length, and is sometimes coasted on each side 

 by a narrow, bistre-coloured stripe. The operculigerous lobe 

 is almost co- extensive with the foot, of a dark red-brown 

 colour, and largely alated ; it is furnished with three densely 

 ciliated, flattish, pointed vibracula on each side ; the middle 

 ones are very short and inconspicuous, each bifid, or formed 

 of two strands : with powerful glasses I have never failed to 

 discover them in all the Exmouth examples, and I believe 

 that three on each side is the normal number. The lobe 

 carries a white, highly polished, subcircular, testaceous pauci- 

 spiral operculum, concave within, convex without, and fixed 

 on the posterior extremity about midway. This animal has 

 the peculiar littorean oscillatory quality of progression, which, 

 with the paucispiral operculum, seem to mark it as a trans- 

 ition genus from the Trochi to the LittoriruK-, we, however, 

 must admit, that by the vibracula and neck-lappets it has 

 a close connection with the Trochidce. I am puzzled about 

 the reproduction, on which account I can only at present 

 refer to the original notes. No exserted verge has been 

 detected, and though placed in our first account, provisionally, 

 with the Trochidte, I rather think, by the character of the 

 operculum, it is bisexual, and that in a comparison of the two 

 genera, the balance preponderates on the side of Littorina. 



It is sometimes infested with a longish, strong, cylindrical, 

 dark brown parasite, with a clavate termination, which hangs 

 to the side of the opercular lobe, and may be mistaken for a 

 vibraculum. 



CAECUM TRACHEA. (P. 327.) 



The tentacula are not short, as originally stated, but com- 



