No. 600] ORNAMENTATION IN THE KILLIFIS HES 



745 



of but slight value. So far as I have been able to examine 

 material, these little spines occur only in certain species 

 of the true killifishes, the pursy-minnows and the four- 

 eyed fishes, or the Fundulina?, Cyprinodontinae and the 

 Anablepinae, respectively. I have never seen any in the 

 top-minnows. It is interesting to note that the four-eyed 

 fishes, creatures with remarkable and extreme modifica- 

 tions of structure, should be the only group of viviparous 

 forms in which the spinules have so far been found to oc- 

 cur. These spinules are different in several ways from 

 the nuptial tubercles of cyprinoids, in that they are more 

 permanent, though very minute and inconspicuous. They 

 may easily be overlooked in preserved examples, owing 

 to the mucus exuded and covering the scales and fins. 

 This should be carefully cleaned away, before they can 

 be detected, and even then only with a good lens. Each 

 spinule is found to arise on or close to the edge of the 

 scale, and not on its exposed surface, as the more dis- 

 tinctly straight conic tubercles of the cyprinoids. The 

 spinules are not always perfectly firm and rigid, but may 

 be flexible or delicate. Those on the anal fin rays are 

 generally curved slightly and are also often close together, 

 though not perfectly regular. Their arrangement or de- 

 sign is usually more or less complete in each species. At 

 least in one species their development occurs in the young, 

 as in the ornatus stage of the common mummichog. Prob- 

 ably the spinules in most species are not permanent, but dis- 

 appear after the spawning-season. However, if the spawn- 

 ing-season for a certain species is protracted, males with 

 spinules may be found for a period of several months. 

 Preserved specimens of killifishes do not show scars or 

 pits like cyprinoids, and it may be that the spinules wear 

 away as well as drop off. I have not found any examples 

 with spinules in cold weather, or when spawning was ap- 

 parently over. In no case have the inner edges of the pec- 

 toral rays been found with spinules, like the tubercles of 

 certain cyprinoids. Doubtless such developments are to 

 be correlated with the spawning habits, as none of the 



