20 NEW-YORK FAUNA. 
GENUS BOLEOSOMA.* 
Two dorsal fins. Opercle scaly, with a single spine. Preopercle smooth on the margin. 
Six branchial rays. Nape depressed, contracted. 
THE TESSELLATED DARTER. 
BoLeosoMA TESSELLATUM. 
PLATE XX. FIG. 57. —(STATE COLLECTION.) 
Characteristics. Small, brownish, with oblong quadrate spots on its back and sides. Length 
two to three inches. 
Description. Body cylindrical, tapering, covered with rough scales, which extend over the 
opercular bones. Scales moderately large for the size of the fish, rounded; truncated and 
plaited in front, ciliate on the free margin. Lateral line tubular, broadly and regularly con- 
cave, nearly medial. Head small. Nape smooth, and depressed at the basal line as if 
strangulated ; thence ascending to the interorbital space, and descending rapidly to the tip of 
the snout. Eyes large, contiguous, 0°12 in diameter, and less than their diameters apart ; 
the space between deeply furrowed. Nostrils double ; the posterior near the edge of the 
orbit, the anterior with valvular margins. Opercle with a pointed membrane behind ; and in 
advance of this, a small but robust spine. The preopercle with a smooth margin, and rounded 
at its angle. Branchial membrane with six rays. Mouth small, terminal, slightly protractile. 
Very minute card-like teeth in the jaws, forming two or more series. Equally minute teeth 
on the vomer, and anterior portion of the palatines. Tongue smooth. No swim-bladder. 
Dorsal fins two ; the first commencing on the anterior third of the head and body; the first 
dorsal with nine spinous rays; the first ray slightly shorter than the second; the third, fourth 
and fifth, subequal, longest; thence gradually diminishing to the last, which is supine, and 
nearly hidden in the depression which contains the fin. The second dorsal fin arises 0°2 
behind this last, and contains fourteen branched rays longer than high ; highest in front, where 
it exceeds in height the spinous dorsal, and gradually diminishing behind, ending beyond the 
termination of the anal. Pectorals pointed, hastate, the tip reaching the end of the first 
dorsal; composed of thirteen rays, the fifth and sixth longest, the inferior ray shortest. Ven- 
trals small, arising posterior to the base of the pectorals ; composed of one simple and five 
branched rays, of which the third is longest. Anal nearly as long as high, composed of ten 
rays, of which the first two are short. Vent under the origin of the second dorsal fin. 
Caudal fin even, and is a powerful instrument, 0°45 in length. 
* From fons, a dart or javelin, and copa, body. 
