616 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxxni. 



end, while at the base of the balancers it forms a well-defined and 

 quite regular ring just inside the margin. 



The posterior half of the body inside of the pigment lines is filled 

 with semiopaque yolk granules of a pale yellow color. 



The balancers are one-fourth the length of the body, slightly 

 curved outward, cylindrical at the base, with a flattened spathulate 

 tip. 



Total length, 0.4 mm.; width of body, 0.23 mm. 



The colors of this nauplius blend finely and make it one of the 

 most beautiful yet seen. 



{pseudorostris , pseudo, false and rostrum.) 



This new genus was obtained from the mouth of the lizard fish, 

 Synodus fatens Linnaeus. The frontal plate, rostrum, and anterior 

 portion of the carapace were buried just beneath the sldn of the roof 

 of the mouth, while the large second maxillipeds were sunk through 

 the skin and into the underlying tissue. This method of fastening- 

 is significant, taken in connection with the fact that the sides of the 

 carapace are folded over ventrally as in LernaifUliropu8,Qi\d the apron 

 of the third legs is so much reduced that it can not fill the gap at the 

 posterior end of the carapace and thus function as a sucker. 



It means that we have here a genus undoubtedly belonging to 

 the Caliginse, but one which has so far degenerated as to have given 

 up those structures which in the other genera function as organs of 

 adhesion. The lunules on the frontal plates, the thin pliable margin 

 around the carapace, and the large apron of the third legs have all 

 disappeared. And what is still more remarkable, in view of these 

 facts, the second antennae, wliich play such an important part in 

 the other genera as grasping organs, have practically disappeared 

 in the female. And the creature is thus throwii back upon the sec- 

 ond maxillipeds alone for retaining its position upon its host. This 

 is a condition obtaining only in the lower families of parasites, and 

 furnishes an excellent example of a reversal of ordinary develop- 

 ment. In many of the specific problems of development which 

 have been so admirably worked out by various scientists, we find 

 prophecies of future advancement. Old organs take new forms, new 

 organs appear, or there is a difi^erent arrangement of the various 

 parts of the body which amounts to very little in the creature under 

 immediate consideration, but which in subsequent development, or 

 in other and higher animals that appear later, becomes an important 

 and essential character. Feathers did not mean very much to the 

 flying lizards upon whose tails they first appeared, but they play 

 an important part in the life of an ordinary bird. So here in degen- 

 eration or the reversal of development we find similar prophecies 

 of future disappearance and loss. 



The habits of the genus are very difi'erent from those of the rest of 

 the CaliginiB, as would be expected from its structure. 



