no. 1404. . PARASITIC COPEPODS—CALIGID.E— WILSON. 615 



known in that genus, the following differences may be noted. First, 

 the carapace is relatively much smaller here and ovate instead of orbic- 

 ular. Again, the free segment or neck is nearly twice as long as in 

 Caligodes, and it is the same diameter throughout, instead of being 

 enlarged where it joins the genital segment. The latter is also very 

 different, having no processes of any kind in Echetus, but simply 

 short and rounded lobes, such as are common in Caligus and other 

 genera. 



The dorsal surface of this segment is also marked by the ridges 

 already described, in a manner totalty unlike Caligodes. Here the 

 abdomen is a symmetrical elongated spindle, while in Caligodes it is 

 broad and flattened, and in the species carangis is produced into poste- 

 rior processes, like the genital segment. In this genus also the fourth 

 legs are different from those in the three species of Caligodes, but the 

 latter differ as much from each other, so that this could hardly become 

 a generic distinction. 



Genus LEPEOPHTHEIRUS Nordmann. 



Carapace large, shield-shaped. Basal joints of the first antennae 

 without the sucking discs characteristic of Caligus/ the terminal joints 

 free. Mandibles toothed only on the inner margins. Second maxilla? 

 small, bifurcate, the branches acuminate. 



First and fourth thoracic legs uniramose, second and third biramose. 

 Free thoracic segment simple, without dorsal plates. Genital segment 

 also simple, without plates or processes. Abdomen one or two seg- 

 mented. The young with a frontal filament during the chalimus stage, 

 as in Caligus. 



(LrjH'ojikt/ieirus, Af7roV, a scab, and (f>6eip, a louse.) 



ARTIFICIAL KEY TO THE SPECIES. 



This key is based upon the different body relations, as in Caligus (see p. 555). The 

 same method of measurement is used as in the former genus, and here also are 

 included all the valid species known at the present time, with the authority for each. 

 The author considers L. obscurus (Baird) to be the male of L. hippoglossi, while the 

 specimen called by Bassett-Smith (1896, plate iv, fig. 2) "Caligus obscurus, Baird," 

 is certainly not identical with Baird' s species, but is probably L. thompsoni (see 

 |i. 622). Three of Krover's "new species," gibbus, gracilescens, and rhombi, are con- 

 sidered identical with I. thompsoni, as are also Malm's I. branchialis and van 

 Beneden's /.. gracilis, for reasons stated on page 622. Of the remaining species which 

 are included in this key there are five which are based on single specimens, namely, 

 cossyphi, longipalpus, molvse, quadratus, and robustus. Another, ornalus, was not very 

 clearly differentiated by Milne-Edwards, and no figure of it has ever been published. 



1. ( 'arapace definitely more than half the entire length 2. 



1. Carapace alum; half the entire length 14. 



1. ( larapace decidedly less than half the entire length 17. 



2. Alul 'ii two-jointed, half as long as genital segment or more 3. 



2. Abdomen t wo-jointed, less than half the genital segment 4. 



2. Abdomen one-jointed, half the genital segment or more 5. 



2. Abdomen one-jointed, less than half the genital segment 10. 



