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BULLETIN OF THE BUREAU OF FISHERIES 



due in part to the presence of heavy pigment deposits bordering the exposed sur- 

 faces of the scales on the dorsal area. The top of the head is cartilaginous white, 

 usually obscured with abundant, fine pigment dots, with four small patches of green 

 lying in the frontal bones on each side of the carina. Three of these patches are 

 situated posterior to the center of the eye and are nearly contiguous, extending back- 

 ward to the occiput. The first is the largest and is rounded triangular in shape. 

 The other patch is situated on the side of the carina and is club-shaped. Its narrow 

 end extends backward and inward to meet its companion of the other half of the 

 head. There is also a small bit of green in the heavily pigmented cartilage on the 

 side of the head in front of the eye. The cheeks are silvery, without color, excepting 

 a small patch of green on the dorsal angle of the operculum. The maxillaries, usu- 

 ally the premaxillaries, preopercula, and mandible are whitish and usually unpig- 

 mented, though all but the maxillaries (not including the jugals) and the preopercula 

 often show a few pigment dots. 



The fins are whitish, translucent, all but the ventrals more or less pigmented. 

 The cranial margin and a wide distal band of the dorsal, the lateral borders, the distal 

 third of the longest and half of the shortest rays of the caudal are smoky to black in 

 hue. The dorsal margin and inner surface of the pectoral often are sprinkled spar- 

 ingly with black. Often pigment dots are present on the membranes that connect 

 the anal rays. 



All color fades after death, and after preservation the silvery tone usually dis- 

 appears, leaving characters of pigmentation more conspicuous. The pigment, which 

 in life is evident on the entire dorsal surface, is revealed in diminished abundance on 

 the sides above the lateral line. Below the lateral line and on the cheeks pigment is 

 scattered. 



Most, if not all, of the males acquire pearl organs in the breeding season. All 

 the males taken off Rock Island, Wis., on August 19, 1920 (record 1), and most of 

 those taken later in that year out of other ports showed pearls. Pearls are present 

 on all the scales, except often on those of the dorsal and ventral surfaces caudad of 

 the dorsal and ventral fins, and also on the four surfaces of the head, including the 

 mandible and maxillary. There are indications on some specimens that faint pearls 

 are developed on at least some of the fins, especially on the abdominal ones. The 

 pearls on the head are smallest, are irregular in shape and size, and are irregularly 

 distributed. With the exception of the dorsal and ventral areas and the scales of the 

 lateral line (where the pearls may be irregular in shape and distribution, unequal in 

 size, and sometimes two or more in number), there is only one pearl on each scale. 

 The lateral-line scales have two pearls each, one on each side of the pore, the two often 

 fusing over it. The pearls on the belly anterior to the ventrals are borne on a 

 somewhat thickened epidermis. On the sides, pearls are well developed on the first 

 three or four rows above the lateral line and on the first five or six below. In shape 

 these pearls are rounded to oval, usually longer than wide, flattened, situated at or near 

 the tip, and extending from one-half to two-thirds the length of the exposed portion of 

 the scale. They are largest on the anterior two-thirds of the two rows on each side 

 of the lateral line, where they occupy one-fourth to one-third of the exposed surface, 

 and diminish more or less gradually in size dorsad, ventrad, and caudad. 



