156 BULLETIN OF THE BUBEAU OF FISHEKIES 



The teeth are likewise different in the two genera, those of Fundulus being sharp- 

 pointed, whereas in Cyprinodon they are wedge-shaped and incisorhke. The 

 two local species of Fundulus are separable by their markings, majalis of all ages 

 being barred with black while the adult heteroclitus is not. 



57. Commou mummichog {Fundulus heteroclitus Linnaeus) ■ 



Killifish; Salt-water minnow; Cobbler; Chub; Mudfish; Mud dabbler 

 Jordan and Evermann, 1896-1900, p. 641. 



Description. — This is a thick-set, stout-bodied fish, about one-fourth as deep as 

 long, its body thickest just back of the head, whence it tapers to the taU. Both 

 its back and its belly are rounded, but the top of the head between the eyes is flat. 

 The snout, as seen from above, is blunt. The mouth is terminal and so small that 

 it does not gape back to the eye. Perhaps the most striking feature of Fundulus 

 is its very deep caudal peduncle and roimded caudal fin. The fins are of moderate 



-i^ 



Fig. 65. — Coiuii.oi. :..Limmichog (Fundulus heteTOditus) 



size, the dorsal being situated behind the middle of the body above the anal. The 

 pectorals are broad and rounded. Both head and body are covered with large 

 rounded scales. In males in breeding condition the scales on the sides of the head 

 and on the flanks below and behind the dorsal fin develop fingerlike processes, the 

 so-called "contact organs," on their free edges. 



The mummichog exhibits a striking sexual dimorpliism in the dorsal and 

 anal fins, which are not only larger in the male than in the female, and the anals 

 of a different shape,^° but more muscular (they are used as claspers in the act of 

 spawning) . 



Color. — Males and females differ in color as well as in the sizes of the fins. Out 

 of breeding season the males are dark greenish or steel blue above, marked on the 

 sides with narrow irregular silvery bars or mottlings made up of a series of dots, 

 and with white and yellow spots. The belly is white, pale yellow, or orange; the 

 dorsal, anal, and caudal fins are dark green or dusky with pale mottlings; the front 



s" A detailed account of the sexual differences is given by Newman (Biological Bulletin, Marine Biological Laboratory, Woods 

 Hole, Mass., Vol. XII, No. 5, April, 1907, pp. 314-348). 



