949 Ayres's Description of a new Species 
descending as low as the base of the operculum. "Two very 
small plates are below the anterior extremity of the pre-oper- 
culum. Between the opercular pieces and those which cover 
the top of the head is a narrow row, consisting of twelve 
small plates. This row commences inimediately behind the 
eye, and extends to the back of the head ; itis gently curved. | 
'The fifth and sixth plates in the row, counting backward, are 
free on their inner border, and form an opening to the back 
of the mouth, an arrange: ent similar to that in the Bichir, 
which was conjectured by Geoffroy de St. Hilaire (Ann. de 
Mus. tom. i. p. 57.) to be a compensation for the imperfect 
mobility of the branchial plates. The inferior surface of the 
head consists of a single plate on each side, narrow in front, 
widest posteriorly ; this plate undoubtedly represents the 
branchial rays of other fishes. 'The whole body is covered 
with hard, enamelled plates or scales which give it a tessellated 
appearance, as the exposed surface of each is rhomboidal. 
The portion by which they are inserted in the skin is pro- 
longed into a tooth-like process, at the base of which another 
is sometimes seen, much smaller. 'The lateral line is straight, 
but is quite indistinct both at its origin and its termination. 
The whole lateral surface of the head, anterior to the pre- 
operculum, and above the branchial plates is covered with 
smooth, soft skin. This by its projection in a fold beyond 
each jaw, forms a wide but thin and almost membranous lip. 
The lip is narrowest in front of the jaws, and its greatest 
width is on the side of the upper jaw, where it is two tenths 
of an inch. On all parts of the head, both the smooth and 
plated surface, are numerous uncommonly large and distinct 
holes for the admission of water. 
About a fourth of an inch anterior to the eye is a barbule 
three tenths of an inch in length. A 
The operculum is provided beneath with a wide membra- 
nous border, which becomes narrower as it mirenda; and-does 
not extend to the upper portion. 
The teeth are very numerous. The upper jaw has a single 
