I could not obtain a glass vessel suitable for an aquarium, so as to keep them alive and observe their habits. The use of the strange maxillary processes or channels is obscure, nothing analogous being known in other fishes, the nearest approach to them being apparently the lengthened maxillaries of some _Salmonidæ_ and _Clupeidæ_, fish of entirely different habits and affinities, this one being evidently one of the _Gobidæ_. The stomach contained small crabs, apparently swallowed whole. PTEROPLATEA Müller and Henle, 1837. _P. marmorata_, Cooper, State Collection, Species 674. [FIG. 25.] [Illustration: FIG. 25.] _Specific characters._—Outline of disk rhomboidal, the anterior borders forming an obtuse angle in front, nearly straight in their course to the lateral angles, which are sub-acute; the posterior borders rounded. Ventrals small, oblong, obtuse-angled, projecting a little behind the disk. Tail nearly twice the length of ventrals, slender and pointed, flattened laterally behind the spine, and bordered by a very narrow membrane, commencing opposite the end of the spine below, and ending a little farther back above. Spine arising at a point one-third the length of the tail from its base, one-sixteenth of its length, and less than a fourth as wide as it is long. Both surfaces are nearly flat. Proportional measurements: Total length of specimen, 9½ in. 100. From median line to tip of pectoral .80 From anterior angle to eyes .13 From anterior angle to ventrals .70 Antero-posterior length of ventrals .10 Length of claspers .04 Length of tail beyond ventrals .25 Length of caudal spine .04 Distance between eyes .15 _Colors._—Thickly marbled with blackish and grayish mottlings equal in size; ventrals and tail with a few scattered white spots; below, white. It is probable that the colors are variable, as in the allied _Urolophus_. I was doubtful at first whether to consider this fish a _Pteroplatea_, as that genus is described by Richardson as having the mouth curved, and the dental plate extending to its corners, also the teeth lobed. These characters, however, may change with its growth, this being evidently a young specimen. Mr. Gill, of the Smithsonian Institution, Washington, D. C., to whom I sent a figure of it, agrees with me in referring it to this genus. Compared with the _P. Maclura_ (Lesueur), of the Atlantic coast, described and figured by Dekay in the Nat. History of New York, this species is less wide in proportion to its length, the difference being as 10 to 16. There is also some difference in the markings. The _P. Maclura_ is said to attain the enormous width of 18 feet.