Fam. 3, Plate 17. 



Fig.l. 

 EOLIS SMARAGDINA, Alder and Hancock. 



E. gracilis, alba, pellucida; capite curto; branchiis elliptico-oblongis viridibus, apicibus albis, 

 fasciculis 5 digestis ; tentaculis dorsalibus et labialibus longiusculis, sequalibus ; angulis anterioribus 

 pedis productis. 



Hab. Among sea-weeds between tide-marks, very rare. Whitley, Northumberland, A. H. 



Body about half an inch long, slender, pellucid, white, with most of the small branches 

 of the gastric system appearing through the skin of a pale green colour. Dorsal tentacles 

 rather long, slender, smooth, and tapering, transparent white, or nearly colourless. Oral 

 tentacles of the same length as the dorsal pair, and equally destitute of colour or markings ; 

 their external bases form the sides of the head, which is very short. Branchia rather large, 

 elliptical, or nearly linear ; the central vessel of an emerald green colour; the tips pellucid, 

 with a slender ring of opaque white. They are arranged down the back in five well-defined 

 clusters. Foot slender, pellucid, produced at the angles into moderately long processes. 



We have taken only one individual of this Eolis. It occurred at Whitley, in June, 1843, 

 crawling upon the common Fucus vesiculosus. This position was most likely accidental ; at 

 least it must not be taken as a proof that the species is less carnivorous than its congeners, 

 for we saw it, during its captivity, seize and actually devour a portion of a living F. gracilis 

 that was in the same glass with it. 



The nearest allies of F. smaragdina must be looked for among the Eolides with red 

 branchiae, as no other green species that we are acquainted with belongs to the same section of 

 the genus. It approaches very near to E. gracilis, from which it differs chiefly in the colour 

 of the branchiae and the shortness of the head. 



