614 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxvm. 



men a brownish yellow, considerably darker than the genital segment; 

 of the egg strings a dark brown. 



(typicus, typical, that is, the type of the genus.) 



The National Museum collection includes three unnumbered lots 

 collected by Dr. H. M. Smith from the inside of the operculum of the 

 common channel bass {Sciaenops ocellatus Linnseus) in the fish markets 

 in Washington city. 



In 1863 Kroyer published the description of some specimens of 

 female copepods which he had obtained from this same channel bass 

 at New Orleans. He called the fish Corvina unimaculata in his manu- 

 script. He states frankly that the parasites had no head and only a 

 portion of the long and slender neck. But they seemed to him so dif- 

 ferent from any of the others he had examined that he established for 

 them a new genus Echetxm, and a new species, typicus. From his fig- 

 ures and description there is no doubt that his specimens were the 

 same as those here described, especially as they were obtained from 

 the same species of fish. The names which he gave have accordingly 

 been adopted, and the genus designation, which has already been 

 explained (p. 611) seems peculiarly appropriate for a creature which 

 burrows into the flesh of its host the entire length of the carapace and 

 long free segment, leaving nothing but the genital segment and abdo- 

 men exposed. 



So firm is the hold which the creature thus obtains that it is impos- 

 sible to remove one entire without cutting away the flesh from around 

 its neck and carapace. Those which Kroyer obtained were probably 

 pulled out without cutting the flesh, with the result that the free seg- 

 ment broke somewhere near the center, to judge by the measurements 

 which he gives. For the obtaining of the head intact upon several of 

 the present specimens the author is deeply indebted to the persistent 

 and careful efforts of Doctor Smith. And the result fully justifies the 

 efforts, for the addition of the head changes entirely the systematic 

 position of the genus and its relationships. Kroyer considered that 

 the portion which he obtained indicated considerable degeneration. 

 He states that "the large knobs on the dorsal surface are, as it were, 

 the beginning of a monstrosity of the genital parts observed in Lernse, 

 hranchialis and L. cyclopterina, and indicates an approximation to those 

 forms." And in accordance with this view he places the species in a 

 group which he designates as Lerngeocerina (Lernseidae), including the 

 most degenerate forms known. But the general arrangement of the 

 various body regions, together with the details of the carapace and the 

 appendages, show at once that it belongs to the subfamily Caligina? 

 now under consideration. It thus takes its place among the least rather 

 than the most degenerate forms. 



It is most closely related to the genus Caligodes, founded by Heller 

 in 1865. On comparing it carefully with the three species ahead} 7 



