235 
12. DEescRIPTION OF A NEW FORM OF LAMPREY FROM AUSTRA- 
LIA, WITH A SYNOPSIS OF THE FAMILY. 
By J. E. Gray, Esa., F.R.S., V.P.Z.S. erc. 
(Pisces, Pl. IV. V.) 
The Lamprey. which I have now to present to the attention of the 
Society differs in so remarkable a degree from any other known spe- 
cies, that, premising that I propose for it the name of Geotria Austra- 
lis (Pisces, Pl. V.), I think it best to connect with the description a 
revision of the whole Family to which it belongs. ; 
PETROMYZONIDZ. 
Nasal aperture closed, and the palate entirely covered with skin. 
Lampredia, Rafin. Anal. Nat. 94, 1818.—Petromyzonide (Petro- 
myzonini), Bonap. Syst. Ichth. 1838; De Kay, Nat. Hist. of New 
York,379.—(F am.) Hyperoartia, Mill. Abhandl. Akad. Berlin, 1836, 
77; Mag. Zool. & Bot. i.406.—Petromyzide, Gray, Syn. B.M.1842, 
148, 150. 
Miller (Abhandl. Akad. Berlin) divided the genera thus :— 
1. Petromyzon, with visible teeth. 
2. Ammocetes, without visible teeth. 
Synopsis of Genera. 
A. Petromyzonina. Teeth distinct ; eyes visible. 
1. Perromyzon. Upper inner teeth two, conical, close together ; 
lower single, crescent-shaped ; labial teeth numerous, conical ; lin- 
gual teeth two, pinnate (Pl. IV. f. 1). 
2. Lamprrra. Upper and lower teeth transverse, crescent- 
shaped; labial teeth in two submarginal rows; inner lateral teeth 
larger, two- or three-lobed, lingual teeth pectinate (Pl. IV. f. 2). 
3. Georria. Upper and lower teeth transverse, crescent-shaped; 
upper lobed ; labial teeth numerous, distant, acute, nermost largest ; 
lingual teeth elongate, conical, arched (Pl. IV. f. 3). 
4. Vexasia. Upper and lower teeth transverse, crescent-shaped ; 
upper two-lobed ; labial teeth numerous, crowded, truncate ; imner- 
most largest ; lingual teeth elongate; arched. 
5. Caracoxa. Upper internal teeth two, farzapart, three-lobed ; 
lower crescent-shaped, nine-lobed ; labial teeth transverse, band-like, 
four tubercles ; lingual teeth flattened (Pl. IV. f. 5). 
6. Morpacta. Upper inner teeth two ; lateral three-lobed ; lower 
nine, conical, in an arched series ; labial teeth conical, in a single sub- 
marginal series ; lingual teeth elongate, conical, arched (Pl. IV. f. 6). 
B. Ammoceetina. Teeth none; eyes hidden. 
7. AMMOC@TES. 
