PARASITIC COPEPODS-CALiaiDJE— WILSON. 581 



carapace. T\\v\ tapei' forward to a sharp point at the l)aso of the 

 frontal tilauient as thoug-h pulled out l)y the latter. The two terminal 

 joints of the first antenna are attached to the posterior l)order of the 

 frontal plates, oivino- them the appearance of heinj^- attached to the 

 lateral maroin of the carapace, well back toward its center (tig. 114). 



The eyes are so far l)ackas to be a little behind the apparent center, 

 though the}^ are not far from the actual anterior margin of the cara- 

 pace! There are no posterior sinuses, the third thorax segment not 

 having yet fused with the head. This leayes the posterior margin of 

 the carapace concayc, the posterior corners projecting somewhat. The 

 third thorax segment is separated by a well-defined groove from the 

 carapace; it is a little wider, but only half as long as the fourth seg- 

 ment, and from its well-rounded sides project the third swimming legs. 



The latter have not yet acquired their broad basal apron, but are 

 almost exactly like the second pair, and the exopods can l)e plainly 

 seen in dorsal view. The fourth segment is long and large, with well- 

 rounded sides; the foiu'th legs are attached near its posterior margin 

 and are quite rudimentary. 



The genital sequent and abdomen are still fused, though the line of 

 separation is indicated l)y a deep indentation on either side. 



The anal lamina^ are small but the plumose seta^ are long and stout. 



The total length of the earliest stages is only a trifle over 2 milli- 

 meters, of which the carapace, including the frontal plate, makes up 

 about four-sevenths. 



This species occurs very frequently and often in great abundance 

 upon the codfish of our coast, l)ut has been rarely ol)served on other 

 species of fish. Most of the specimens in the collection of the National 

 Museum agree closely with the Qd'ujuH americaniix^ so w'ell described 

 by Pickering and Dana (1888). 



But there are a few lots of females in which the abdomen isl)roader 

 and more nearly quadrangular. A careful examination of these 

 specimens, however, fails to reveal the slightest ditt'erences in the 

 appendages and hence they can not be regarded as even a yariet3\ 

 This is one of the species upon which MiiUer founded the genus 

 Caligu^ in 1785, and is the only one of the types which has proved to 

 be a real C(dlgu><, the others belonging to other genera. Hence the 

 present species is left as the sole type of the genus. 



Man}" lots of specimens have been obtained by the United States 

 Fish Commission from codtish taken along the New England coast 

 from Maine to New York, and on the ofl'shore fishing banks. They 

 are exceedingly abundant during the autumn of the year when the 

 shoal- water fish are l)rought into the local markets, and they gradually 

 diminish as the season advances. They are most numerous on half- 

 grown fish and may be found anywhere upon the extei'nal surface or 

 the fins. They are also rarely taken in company with ( /. rapa.e in the 



