HEMIGALEUS. 149 



below the eye, front end little higher. Pectorals large subfalciform, angles 

 blunted, hind margin concave. Dorsal origin a short distance behind the base of 

 the pectoral, upper angle sharp, hinder produced. Ventrals small, nearer to the 

 second dorsal than to the first. Second dorsal and anal subequal, former slightly 

 in advance of the latter, hind margin nearly straight; anal little smaller and 

 extending little farther back, hind margin deeply notched, base distant twice its 

 length from the caudal pit. Caudal long, slender, pointed, subcaudal lobe 

 produced, sharp, length of fin varying from about one third of the total in the 

 young to one fourth or less in adults. The number of rows of teeth also varies 

 among individuals; some large ones at hand have but 21 rows while others, and 

 much smaller, have 25 or 23 rows. The measurements of a very small specimen 

 are total length 23, snout to hindmost gill opening 4§, snout to abdominal pores 

 lOf, and caudal fins 8j inches. 



Young light brownish with numerous irregular spots of darker along the 

 sides of body and fins, the spots fusing more or less into vertical bars on the sides 

 or transverse bars on the fins, the markings fading with age as the brown darkens 

 until the appearance is uniform greyish brown. 



Tropical and temperate seas, to 70° degrees or more from the equator. 



Hemigaleus. 



Hemigaleus Bleekeb, 1852, Verh. Bat. gen., 24, Plagios., p. 45. 



Form elongate, slender. Head depressed, flattened below. A small 

 spiracle. A nictitating membrane. Mouth with distinct labial folds. Teeth 

 unlike; upper oblique, with denticles on the basal part of the outer edge; lower 

 more erect, with a narrow cusp on a broad base, without denticles. First dorsal 

 opposite the space between pectorals and ventrals. Tail with caudal pits, a 

 notch behind the subcaudal fin and a prominent subcaudal lobe. Spiral valve 

 of intestine with comparatively few transverse turns. 

 Snout broadly rounded 



gill openings less than the length of the orbit 



caudal longer than the space between the dorsals pectoralis (page 150) 

 gill openings wider than the orbit 



caudal equal the interdorsal space . . microstoma (page 151) 

 Snout tapering, rather pointed 



gill openings much wider than the orbit 



caudal equal the interdorsal space . . macrosloma (page 151) 

 gill openings twice the width of the orbit- 

 caudal shorter than the interdorsal space . balfouri (page 152) 



