652 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxvm. 



enlarged .second niaxillipeds, and the fonrth legs. The latter have the 

 same detail as in tlie female, but reach well beyond the posterior margin 

 of the basal abdominal joint. 



Total length 3.7 nmi. Length of carapace 2.2 mm. ; width of same 2 

 mm. ; length of genital segment 0.7 mm. ; length of abdomen 0.54 nnn. 



Color, a dark-brownish yellow, without pigment spots. 



{teres^ smooth, well rounded.) 



The National Museum collection includes two lots of this species, one 

 of twenty-tive females and two males taken from a C'aJlorJtyncJixs^ and 

 the other of about the same number taken from a ray, both at Lota, 

 Chile. The ra}' and the chimjera were in the same tub of fish, so that 

 it is very possible the parasites may have crawled from one to the other. 

 This is a very clean-looking species, and the roundness of its outlines 

 gives it both grace and sjaiimetry. It may be easily distinguished 

 from other species by the rounded barrel shape of the genital segment 

 and abdomen, and by the concave sides of the free segment. This 

 preliminary diagnosis ma}" then lie verified by the presence of toothed 

 lamiuiv at the bases of tlie spines on the fourth legs. 



In 1840 one Claudius Gay published what he styled Historia fisica 

 y politica de Chile, which was issued at Madrid and contained, among 

 other things, a review of the animal and plant life of the country. The 

 author has been unable to find a copy of the text of this work, but in 

 the volume of plates there is a figure" of a parasitic copepod which is 

 designated Call<jus gayi. This was found upon an imdetermined fish 

 and resembles the present species in many particulars, but there is still 

 enough difi'erence, particularly in the coloration, to render it certain 

 that the two are distinct species. 



CALIGUS CENTRODONTI Baird. 



Plate XXVII. 



CaUgus centrodonfi Baird, 1850, p. 272, pi. xxxii, figs. 6 and 7. — Bassett- 

 Smitii, 1899, p. 447. 



Female. — Carapace considerably more than twice the length of the 

 rest of the body, and quite strongly narrowed anteriorly. Frontal 

 plates large and distinct, with a deep central incision; lunules large, 

 circular in outline, and not projecting much beyond the anterior mar- 

 gin. Posterior sinuses of medium depth, nearly parallel, and well 

 rounded; median lo))e a little more than half the entire width, and 

 squarely truncate or slightly emarginate posteriorly. Thoracic area 

 large and ver}' well defined but with indistinct digestive glands. 



Kjv^s situated far forward and entiridy separated from each other 

 but very close togotlici'. th(^ axes slightly inclined toward each other 

 anteriorlv. 



"Plate III, fig. 12. 



