NO. 3574 COPEPOD CRUSTACEANS — LEWIS 91 



uniramous). These characteristics plus the kmule-like structure are 

 also found in Caligus. The lunule-like structure, however, is not iden- 

 tical with that of Caligus and other lunule-bearing genera (see below). 

 The species differs from the majority of the species in Lepeophtheirus 

 for the following reasons : 



1. Part of the frontal region is modified to form a lunule-like 

 process. 



2. The foiu-th thoracic legs are 3-segmented, not 4-segmented, 

 although Lepeophtheirus does include some species with 3-segmented 

 fourth thoracic legs (e.g., L. watanabei Shiino, 1954d). 



3. There are 4 terminal spines on the fourth thoracic legs instead 

 of 3. 



4. The endopodite of the first thoracic legs is larger than in most 

 members of the genus. Many authors state that the first and fourth 

 thoracic legs are uniramous in Lepeophtheirus (e.g., Wilson, 1905b, 

 Yamaguti, 1963). The endopodite of the first leg of members of 

 this genus is reduced or rudimentary but it is present (e.g., L. dissimu- 

 latus Wilson, 1905b; L. gonistii Yamaguti, 1936a) and the leg is 

 biramous. 



5. The postoral process is reduced, especially in the male. 



The lunule-like structure of L. jallolunulus is formed of the upturned 

 lateral anterior surface of the frontal region. Further, the structure 

 is partially separated from the rest of the frontal area and has a 

 strongly denticulated membrane instead of the frilled membrane found 

 on the rest of the region. In Caligus and other lunule-bearing caligoids, 

 the lunule is formed of part of the membrane found on the leading 

 edge of the frontal region. In these, however, the membrane is ei- 

 ther formed around a sinus in the frontal region or it itself forms a 

 sinus. This structure can be sunple (e.g., C. enormis Wilson, 1913) 

 or the membrane can be well developed and the sinus remain open 

 (e.g., C. zei Norman and Scott, 1906), or the membrane can be well 

 developed, the sinus closed, and the lunule of a distinct cup shape 

 (e.g., C coryphaenae Steenstrup and Liitken, 1861). In all cases, 

 however, the lunule is associated with some type of sinus and is di- 

 rected ventrally. In L. jallolunulus there is no sinus, the structure is 

 directed dorsally and not ventrally, and it is found onl}^ on the female. 



In several characteristics, the species is similar to some members 

 of the genus Anuretes and the genus Pseudoanuretes. Anuretes par- 

 vulus Wilson, 1913, resembles this species in the general shape of 

 the fourth pedigerous segment and genital segment, aniennule, and 

 maxilliped, but it differs in the less distinct abdomen, the absence of 

 the lunule-like structure, the reduction of the female postantennal 

 process, the reduction of the sternal furca, and in the nature of most 

 of the appendages. The 3 small, spinelike projections present on 



