226 PENTACT.E. 



drical shape, slightly bulging at the extremity. The in- 

 testinal canal is of moderate length, and its coats are very 

 tender. The branchial tree is not very complex, and has 

 no sacs attached to its trunk. The generative tubes are 

 comparatively few, not exceeding fifty, and are short and 

 white. The skin is coriaceous, and the muscular tunic 

 thin. 



When dredging on the west coast of Ireland with Mr. 

 W. Thompson, Mr. Ball, and Mr. Hyndman, in the sum- 

 mer of 1840, we took a great number of this handsome 

 species, many as large as four inches, and all presenting the 

 external characters described above. It appears to be 

 rather an apathetic species, and to have scarcely any power 

 of retracting its suckers ; but this may have been owing to 

 a circumstance which is of no small interest to both zoolo- 

 gist and geologist. The Lough of Killery, in which we 

 found it, is a narrow and long inlet of the sea. To- 

 wards the upper part of it, whilst the under- water is salt 

 and full of truly marine animals, the surface-water is so 

 fresh that our boatmen were used to drink it. The con- 

 sequence was that in drawing the dredge through the layer 

 of fresh water the contained animals were paralysed, and 

 many observations which we had planned to make upon 

 them were thus unexpectedly defeated. 



