ART. 10 NOTES ON MYCTOPHINE FISHES — PARR 37 



as already made out in the original descriptions of these species, but 

 also in D. chrysorhynchus ^* Gilbert and Cramer, 1897, and D. wata- 

 sei,^^ Jordan and Starks, 1904, makes a new key to this group of the 

 genus Diaphus desirable. 



I. Supraorbital organ short, triangular, entirely in advance of the vertical from 



the center of the eye. Upper autorbital moderate or rather large. 



A. PLO much nearer to the lateral line than to the base of pectoral fin. 

 Head comparatively large, its length equaling 29-31 per cent of the total 

 length without caudal fin. Diameter of eyes 8.1-8.7 per cent of the same 

 measurement, or about S.-^S.G in the length of the head. Upper SAO and 

 Pol close below the lateral line. AO 6+5-6. 



D. chrysorhynchus Gilbert and Cramer, 1897. 



B. PLO much nearer to the base of pectoral fin than to the lateral line. 

 Head smaller, its length only equal to about 26 per cent of the total 

 length without caudal fin. Diameter of eyes about 6.5 per cent of the 

 same measurement, or about 4 in the length of the head. Upper SAO and 

 Pol more than 2 diameters below the lateral line. AO 7+5. 



D, watasei Jordan and Starks, 1904. 



II. Supraorbital long and slender, extending to or beyond the vertical from the 



center of the eye, " in the form of a narrow streak." Upper antorbital 

 small. 



A. PLO only veiy slightly below midway between the lateral line and the 

 base of pectoral fin, its distance above the latter equaling about % of its 

 distance below the fonner. Eyes about 3.8-4 in head. 



D. anteorbitalis Gilbert, 1913. 



B. PLO nearly twice as far from the lateral line as from the base of pectoral 

 fin, the ratio between the two distances being as 16: 9. Eye about 4%-5 

 in head. 



D. adenomus Gilbert, 1905. 



DIAPHUS CHRYSORHYNCHUS Gilbert and Cramer, 1897 



Diaphus chrysorhynchus Jordan and Jordan, 1922, Parr, 1928, Fowler, 1928. 

 Myctophum {DiapJms) chrysorhynchus Brauer, 1906. 



Material investigated. Type sample No. 47710, U.S.N.M. (6 

 specimens). 



The original definition and figure of this species (Gilbert and 

 Cramer, 1897, p. 409 and pi. 38, fig. 3)'*' being in many respects inade- 

 quate for proper identification, it has been deemed advisable to 

 render a full description and diagrammatic illustrations of the 

 essential features observed on the type material. 



'^ See Parr, 1928, p. 120, key to the genus Diaphus, division 9. 



i^Ttiis species has in the previously rendered key (Parr, 1928, p. 122) been identified 

 with D. coeruleus Klunzinger, according to the precedent set by Gilbert, 1913. 



>« In Gilbert and Cramer's report the figures 2 and 3 on plate 38 and the corresponding 

 references in the text have, by misprint, become exchanged for each other, figure 2 actually 

 representing Myctophum fliulatum and figure 3 Diaphus chrysorhynchus, while the 

 legends and references have these species in the opposite arrangement on the plate. 



