348 , 



the aspect of having a narrow upper lobe separated from the 

 pedal disk, forming a pair of narrow labia ; the upper posterior 

 portion of the operculigerous membrane in this species is 

 very slightly expanded laterally, and though not emarginate 

 with caudal appendages, as in Littorina pallidula, is often 

 sinuated and sometimes finely cloven. The operculum is 

 nearly the shape of a vertical section of a pear, brown horn- 

 colour; nucleus sublateral, leaning on the columella, with 

 about 2| gyrations, the last of which rapidly coalesces with 

 the outer margin of the plate. The animal has the true alter- 

 nate undulatory longitudinal characteristic progression of the 

 Littorince. The neck is simple, without lobes. The branchial 

 plume is single, on the left side, with 35-40 or more very fine 

 long close-set pectinations, many of which in certain positions 

 of the animal may be seen under the mantle without dissec- 

 tion. The orifice of the anus and the canal of the sac of 

 viscosity are seen on the right side ; in the female the matrix 

 and its orifice, with the anterior part of the ovary, and in the 

 male, the verge. The fsecal pellets are pale red and exactly 

 oviform : I allude to this point, as I have sometimes found it 

 a good distinctive aid. 



I have mentioned rather more than can be seen without 

 dissection; and I will only enter so far on the anatomy of 

 this species as to observe, that I have carefully compared 

 numerous specimens of the L. littorea, L. pallidula and L. lit- 

 toralis, and I can pronounce all the internal organs, including 

 the oesophageal ganglia, to be absolutely identical, allowing 

 for the modifications of colour in the different species. The 

 male organs generateur supplies the position of the matrix in 

 the female, and the testis that of the ovary; the former springs 

 under the right tentaculum, and is composed of two portions, 

 the basal one being a tumid, annulated or rigid figure, den- 

 tated exteriorly, with the minute orifice at the external angle ; 

 the other angle is produced into a yellow, conical, arcuated, 

 pointed, rather long process, the only use of which would 

 appear to be that of an organe excitateur. 



