248 



the substance of the thin outer coat, giving it a very peculiar ap- 

 pearance. 



The shell on the newly hatched animal, which remains as a nu- 

 cleus on the coat of the older shells, is smooth, uniformly convex, 

 without any appearance of the anterior truncation or of the radiating 

 ridges, which is so peculiar in the adult shells ; and it seems also to 

 have a straight lower edge without any appearance of the large ven- 

 tral gape of the genus. 



The cavity of the tube is contracted by an internal ring just above 

 the hinder end of the shells, leaving an oblong central aperture of 

 about half the diameter of the tube. This contraction is formed of 

 several shelly plates with interspaces between them. 



The animal has the power of repairing a fracture of the tube. 

 There is a specimen in the Museum which had evidently been com- 

 pletely broken across about half its length, and the direction of the 

 tube altered ; the two portions have been united by an internal irre- 

 gular white shelly coat. 



EXPLANATION OF PLATE XXXIX. 



Fig. 1. Furcella gigantea, half the natural length ; a, b, c, d, e, the remains of 



former closing of the tube. 

 Fig. 2. Furcella gigantea, view of terminal closing of the tube ; of the natural 



size. 

 Fig. 3. Palettes, showing the inner and outer sides. 

 Fig. 4. Chcena annulata, enlarged. 

 Fig. 5. Chcena tessellata, enlarged. 



3. Review op the species of the Fissirostral Family Mo- 

 motidjE. By Philip Lutley Sclater, M.A., F.Z.S. etc. 



(Aves, PI. CXXVIII.) 



Considerable additions have been made of late years to this rather 

 peculiar family of birds, of which one member only was known to 

 Linnaeus ; and there are now at least sixteen or seventeen different 

 Motmots, of which examples occur in European collections. Two 

 or three very interesting articles have been written upon the habits 

 and certain structural peculiarities of these birds ; but no modern 

 writer except Lesson, in his little-known volume, entitled ' Description 

 des Mammiferes et Oiseaux ' (where descriptions of eleven species 

 known to the author are given), has attempted a complete review of 

 the species. The following paper has been drawn up with a view to 

 meet this deficiency, and to bring together in one place short cha- 

 racters sufficient for distinguishing these birds, so as to obviate the 

 necessity of referring to all the different publications where the species 

 were originally described. 



Latham's term Momotus, being long precedent to Illiger's Prio- 

 nites, which is sometimes employed for this group, has every claim 

 for adoption. I therefore propose to call the group Momotidce (as 



