54 
PACIFIC SCIENCE, Vol. XIV, January I960 
Fig. 4. Photomicrograph of section showing two 
luminous organs on the flank of E. lucifer. (X ca - 
350). ed, Epidermis; i, iris; lc, lens cell; pc, photo- 
genic cell; ps, pigment sheath. 
characteristics, concluded that Apogon margina- 
tus should be a synonym of A. ellioti. In their 
key to the species of Etmopterus, Bigelow and 
Schroeder (1957: 61) utilized the black mark- 
ings on the flank which include the heavily 
dotted pigment cells of the luminous organs. 
Judging from the results of the present study it 
seems likely that the distribution of luminous 
organs, especially those on the flank and caudal 
peduncle which form peculiar markings, serves 
as one of the specific characters of the genus 
Centroscyllium. 
Attention should be called to the curious place- 
ment of luminous organs on the ventral surface 
of the upper eyelid. The situation of these or- 
gans is similar to the series Li of Chauliodus 
sloani Schneider described by Tchernavin (1953: 
68). The latter consists of 4 T 6 cup-shaped or- 
gans situated within the fold of skin above the 
eye. The role of these organs is unknown, but 
Tchernavin (1953: 68) suggested that such 
orbital photophores serve to illuminate ap- 
proaching prey or to excite the eye. 
SUMMARY 
1. Centroscyllium ritteri Jordan and Fowler, 
like the other species of Centroscyllium or Et- 
mopterus, is provided with a number of minute 
luminous organs on the body surface. 
2. The densely distributed areas of luminous 
organs agree well with the jet-black color pat- 
tern marked on the body, especially those on 
the ventral surface of the upper eyelid, belly, and 
flank. 
3. Each luminous organ is composed of the 
photogenic cells, an irislike structure of pigment 
cells, the lens cells, and a pigment sheath. 
REFERENCES 
Bigelow, H. B., and W. C. Schroeder. 1957. 
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1-150, 4 pis, 16 figs. 
Burckhardt, R. 1900. On the luminous or- 
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Dahlgren, U, and W. A. Kepner. 1908. A 
Textbook of the Principles of Animal His- 
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New York. 
HANEDA, Y. 1950. Luminous organs of fish 
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IwAl, T, and H. Asano. 1958. On the luminous 
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Yokosuka City Mus. (3): 5-13, 4 figs. 
Matsubara, K. 1953. Revision of Japanese 
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Mem. Coll. Agric. Kyoto (66) : 21-29, 3 figs. 
Ohshima, H. 1911. Some observations on the 
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Schmidt, P. J. 1931. Fishes of Japan collected 
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Tchernavin, V. V. 1953. The Feeding Mech- 
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