630 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxvin. 



being that the pigment is confined to the posterior two-thirds of the 

 body, with traces also in the antennules. The eye and brain are dis- 

 tinctl} T bilobed, each half semilunar in shape, the two convex sides 

 facing each other and fused at their centers, giving the whole very 

 much the shape of a rough H. 



Total length 0. 5 mm. ; width 0. 26 mm. 



After the first moult the larva becomes decidedly ovate, the pigment 

 increases considerably in area, the eye moves back from the anterior 

 edge of the carapace, and through the skin at the posterior end of the 

 body can be seen the segmentation and the rudimentary legs' of the 

 metanauplius stage. 



Chalimus. — Carapace elongate and spindle-shaped; frontal plates dis 

 tinct and projecting strongly, giving the anterior portion of the body 

 a triangular outline; the frontal filament at the apex of this triangle 

 large and strong. The anterior portion of the carapace is considerably 

 narrowed. The posterior sinuses are also narrow and not very deep. 

 The median lobe is seven-tenths of the entire width and projects for 

 three-quarters of its length behind the small lateral lobes. The trans- 

 verse groove of the carapace is only a short distance in front of the 

 posterior sinuses, leaving the cephalic area much larger than the 

 thoracic, in spite of the great development of the median lobe. Eyes 

 showing yet as two distinct half moons fused on their convex sides, 

 and situated at some distance from the anterior border. Free seg- 

 ment as wide as the segments posterior to it and quite long; genital 

 segment and abdomen fused into an elongate ovoid, showing by a 

 slight constriction near the center where the two are to separate; 

 anal papillae large and well provided with stout setas (fig. 258). 



Color a pinkish yellow with pigment spots of the same purple as in 

 the nauplius and adult, rather sparingly and irregularly scattered over 

 the posterior two-thirds of the carapace; almost none anywhere else 

 on the body. 



Total length 2.55 mm.; length of carapace 1.52 mm.; width of same 

 1 mm. ; length of remainder of body 1 mm. 



This is undoubtedly the species mentioned by Smith (1874, p. 281) 

 as found upon the flounder, Ghsenopsetta ocellaris, and which he desig- 

 nates as "a species with a veiy short tail, and approaching Heller's 

 genus Anuretes." It is fairly common on the four-spotted flounder 

 (Paralichthys oblongus), but is not often found upon the summer 

 flounder. It affords a notable example of color protection, for the 

 pigment spots with which it is covered give it so nearly the hue of 

 the dorsal surface of its host that it can be distinguished only when in 

 motion. 



It is always found upon the external surface, and so far as observed 

 always on the dorsal side of the body. It shows no decided preference 



