418 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxxii. 



The newly hatched larvae are sluggish and move about slowly like 

 those of americanus^ but they do not stick to the bottom of the dish 

 like the latter. Moreover, their motion is not jerky and cyclops-like, 

 but is similar to that in the adults. They are beautifully transparent, 

 the small amount of pigment present only serving to bring out more 

 clearl}^ the internal anatomy. The following is a description of these 

 larva^ : 



Carapace broadly elliptical, the width to the length in the propor- 

 tion of 13 to 10; anterior margin broad and rounded, with a fringe of 

 long cilia, among which are scattered tactile hairs; as in other species. 

 The posterior sinus is broad and shallow, while the free thorax and 

 abdomen form a wide triangle relatively shorter than in other species. 

 The first free segment is considerably less than balf (five-thirteenths) 

 the width of the carapace; the remaining segments and the abdomen 

 diminish regularly in size. The abdomen is relatively smaller than in 

 any other species; its shape is that of three-quarters of a circle, the 

 chord forming the base, while the diameter is considerably less than 

 the width of the last thorax segment. 



The anal laminee are close together, small, slightly divergent, and 

 each carries two or three spines, of which the inner is the longer. 



The first antennfe are three-jointed, the two terminal joints approx- 

 imately spherical, the basal joint large and armed with a powerful 

 hook. The curve of this hook reaches to the tip of the terminal joint, 

 while in the amerieamis larva it scarcely reached the center of the 

 second joint. 



The second antennae are similar to those of the fol'iaceus larva, but 

 the two joints of the basal portion are very unequal, the distal one 

 being fully twice as large as the proximal. 



The temporary exopod is without joints and of the same length as 

 the endopod, while this. latter, which is permanent, has three joints 

 increasing regularly in length, the terminal one the longest and tipped 

 with a short curved claw and a pair of bristles. 



The temporary mandibular palps are situated as far forward as in 

 the amerieamis larva and are three-jointed. The spine connected with 

 their base is outside of the mouth tube, straight instead of curved, 

 and much nearer the mouth opening than in other larvae. In fact, the 

 tip of the spine is almost on a level with the rim of the mouth opening. 



The anterior maxillipeds are stout and four-jointed and terminate 

 in the usual pair of sickle-shaped claws, the dorsal one of which is 

 barbed. The large cells in the basal joint which are to form the 

 sucking disk are not apparent when the larva is first hatched, but can 

 be seen forming two or three days afterward. The posterior maxilli- 

 peds are large and five-jointed, each joint armed on its ventral surface 

 with spines and bristles. The terminal joint ends in two small and 

 strongly curved claws and a conical papilla, tipped with a single minute 

 spine, which frequently gets broken off. There is a stout spine on the 



