428 Illustrations in British Oology. 



poetry and prose: but it has been so ably and admirably 

 commenced by a gentleman [Mr. Main] so very far more 

 competent (Vol. IV. p. 118. and 412.), that I will not even 

 presume to play a second ; but leave him with a Tasto solo, 

 ad libitum ; praying him to proceed as he has begun ; most 

 honestly confessing my far greater pleasure in enjoying his 

 acute and well-defined notes, than seeing in print my own 

 inferior accompaniments. 



Mai/ 1. 1832. John F. M. Dovaston. 



Westfelton, near Shrewsbury. 



Art. VI. Illustrations in British Zoology, By George John- 

 ston, M.D., Fellow of the Royal College of Surgeons of Edin- 

 burgh. 



4. E^OLIS RUFIBRANCHIA^LIS. (fig. 85.) 



CI. Gasteropoda, Ord. Nudibranchia, Fam. Glaucidae, Gen. E'olis. 



, The genus E'olis, Eolida, or Eolidia, (for thus variously is 

 it written,) was established by Cuvier, when this great master 

 in natural science first undertook to give to molluscous animals 

 an arrangement, in which the various families should stand 

 according to their relations, as indicated by their structure and 

 habits, and which, in its practical application, has as much 

 facility as the most incongruous methods of any of his pre- 

 decessors. The genus embraces such naked sea-snails as 

 have two or three pairs of conical non-retractile tentacula at 

 the head ; and external branchiae, in the form of tapered 

 slightly compressed filaments or papillae, disposed in one or 

 more rows along the back. The skin covers the body closely, 

 and nowhere assumes the form of a cloak ; and the little 

 creatures move along solely by the undulations of the foot, 

 which, like that of the slug, forms the entire under surface. 



In illustration of the genus, I select a species which, it 

 appears to me, has not hitherto been described, and which 

 may be distinguished by the following character : — 



